They were designed and constructed by Robert Day, the author of this manual and former graduate student in the Department of Ecology, Evolution and Organismal Biology, with the assistance of various undergraduate students and technicians, particularly Heather Bailey and Heather Hines.Day eventually departed the EEOB graduate program to pursue a PhD in Science Education in OSU's School of Teaching and Learning.
Maintaining the microcosms is a major responsibility not to be taken lightly. It requires relentless dedication and commitment as well as a real love of the aquarium hobby. You will face frustration, floods, late night emergencies, occasional personal expenses and very little recognition. You will need to make routine maintenance part of your daily ritual. You must be a manager, ecologist, vet, engineer, teacher and advocate. You must be ready to treat the microcosms like one of your own children and be ready to provide for their daily care if you are ever absent. This may sound overly alarmist. Believe me it's not. Still interested ? I hope so, because there is an up side. As you meet and overcome new problems, become familiar with the multitude of inhabitants and their place in a dynamic community, and see the students get really excited about studying biology, you may find yourself learning more about, aqua culture, ecosystem management and science education than you have learned in any of your formal classes. I hope you will ultimately find the experience as rewarding as I have during my time at Ohio-State. It's true that you will end up donating a lot of time to the department, but at the same time, the department is subsidizing your hobby, and helping you gain valuable experience in a field where few opportunities exist for the inexperienced. Like many of the specimens you care for, you and the department will be locked in a truly symbiotic relationship. You will not be totally alone, since the world is full of aquarium enthusiasts. I have developed a network of local contacts who will be happy to help you, and I will try to make myself perpetually available to answer questions at any time in the future. Please try to keep a note of my whereabouts through the years in the back of this manual. Good Luck.
If you are not already familiar with the basics of modern aquarium science, it is recommended that you read the entire manual carefully, and watch the accompanying video before attempting to work with any of the displays. The manual assumes that the reader has a general background in biology to at least the undergraduate level.
Even if you are familiar with aquarium maintenance you should still pay close attention to the sections that describe the set up and suggested maintenance schedules of our systems. It is also strongly recommended that you pay particular attention to the section "The twenty most valuable pointers to success when using a microcosm as a teaching aid". This section outlines some of the major differences between the general philosophy of most hobby aquaria, and the quite different approach to be used when maintaining a microcosm as a permanent teaching aid in college classes.
After you have read the manual thoroughly, you may find computer searches for key words useful as a quick reference tool. Important technical terms are often defined as they are used in this manual near where they first appear. Some important definitions appear in more than one section. Other authors may disagree with my semantics, so wherever possible I've tried to explain alternate definitions or terminology that you might come across in the literature.
Keep in mind that ideas expressed in this manual are just one scientist's opinion, or represent ideas that have been found to work in our particular displays through years of trial and error. It may be that you can think of better ways to run the tanks, or perhaps you will construct new displays that will not necessarily follow the guidelines given here. That's fine of course, so long as the displays work, and continue to serve the purpose of educating Ohio State's students as effectively as possible.
Feel free to upgrade and expand the manual, particularly if new displays are added to the collection. Be especially careful to try to upgrade "useful addresses" and the collection of aquarium specimen slides that are kept in the carousels in room 129.
It is recommended that you NOT delete original material from this manual, even if you are already a competent aquarist, or if you decide to discontinue some of the displays, because it may be that your successor will need all the information given in the original manual. (Keep an original back-up disk somewhere safe.)
An aquarium may include fish and plants. The system is mainly controlled by human activities but unpredictable natural phenomenon that affect species diversity may be tolerated. Some attempt is made to make the display look natural, but specimens still generally need to be replaced when they die. Animal inhabitants tend to occupy a measurable proportion of the total available volume.
An ecosystem is a self-sustaining, dynamic community of plants, animals and protists arranged in a food chain, usually powered by light. Humans have little ability to predict how species diversity will change through time because the system is essentially chaotic. Although subject to immigration and extinction, species are present as reproductively independent populations. Individuals do not need to be replaced when they die. Inhabitants typically form a "pyramid of biomass" where plants are common but animals occupy a negligible proportion of the total available volume. A human-initiated, enclosed ecosystem is sometimes called a microcosm (Adey, 1991). Microcosms are excellent models of natural ecosystem
2) Try to keep specimens in a microcosm that closely resembles their natural environment. Maintain strict adherence to ecological principles in all aspects of microcosm design and management. When specimens feel at home and have access to their natural diet, they behave more naturally, reproduce more readily, experience less stress, maintain a more effective immune system and live longer and healthier lives than they would if kept in a sterile or unatural habitat.
3) Each system should mimic a real world food-chain. This typically includes abundant primary production, driven by a powerful light source. Most captive systems will need the equivalent of five to ten watts of fluorescent lighting for each gallon of volume. Commercial aquarium hoods usually supply far too little light to create the primary production necessary to allow a system to be fully self-contained, therefore most of our displays have a customized light source and make use of as additional natural sunlight wherever possible. Alternatively, an enclosed ecosystem might be powered partially or completely by the import of organic material (food). An example would be the decomposer-based "leaf-litter" community in room 129 which relies on the continuous import of energy in the form of decomposing plant material harvested from other displays.
4) Healthy microcosms are very biologically productive and therefore accumulate organic sediment faster than a "fish tank". A little organic sediment on the floor of your microcosm is desirable as a habitat and nutrient source for some species. In nature, this sediment gradually accumulates into vast layers, but because microcosms have limited volume, this is one natural phenomenon that we cannot allow indefinitely. The best way to counter sediment accumulation is to occasionally vacuum or scoop out the excess. This may remove some nutrients and trace elements from the system. You can replace these using either natural composting and the return of compost drainage water, or by the addition of nutrients in the form of commercial "plant food" (nitrate / phosphate based fertilizer) or commercial aquarium trace elements. The practice of adding plant food flies in the face of mainstream "fish tank" maintenance dogma which generally preaches the importance of NOT introducing nitrates or phosphates. A fish tank is not a real ecosystem and does not use nutrients anything like as quickly as a healthy microcosm. I therefore recommend you occasionally add nutrients to all your systems, especially if plant and macroalgae growth seem limited. It makes a big difference to productivity and diversity. Chemical testing reveals that supplemental nutrients vanish from the water and enter the food chain almost immediately.
5) Use physical sub-division and replicate systems as a substitute for the size of the real world. Three different one-gallon systems will hold a greater total number of species than a single three-gallon system. Physical diversity produces biological diversity. Try to include wet, dry, bright, dark, rocky and muddy areas in the same microcosm. Nested systems (microcosms within larger microcosms) and separate but interconnected systems also work well. Resist the temptation to put vertebrates in every system. They tend to eat almost everything, reducing diversity. Walter Adey's research at the Smithsonian stresses the importance of isolated sub-divisions of his microcosms that are free from predation by vertebrates. He calls these areas "refugia".
6) Choose specimens that are independent, hardy and reproductively successful. Try to maintain breeding populations, not single individuals. Avoid endangered, delicate and highly artificially derived (ie. domestic or "ornamental" ) organisms. The latter teach students much less about the mechanisms of natural selection and behavior than "real" animals. Don't ignore the small organisms - that's where most of the diversity is. Students should be taught to appreciate this with hand lenses and microscopes. Don't forget that you need more producers (plants) than consumers, so choose plants that will grow and spread quickly. You can always prune them back if they start to occupy so much volume that they exclude other species. If possible, plants should occupy a significant amount of the total microcosm volume. Animals should not. This recreates the pyramid of mass seen in nature. Watch successional events and don't let any one species become too ecologically dominant. If you think you see an unexploited source of food, try to add a new species that will eat it.
7) Multiple small collecting trips from many sites work better, and are less likely to impact the environment than a large collection trip to a single site. Add tiny, diverse samples from local ecosystems often. This represents the constant immigration of new colonists, a common occurrence in nature.
8) We are in the midst of a global environmental crisis. Set an example by maintaining the tanks in an environmentally friendly way. Talk to students about environmental implications of the microcosms and your collection techniques. Help students to value the diversity of living things.
9) Never think of, or refer to the microcosms as "fish tanks". This idea is as outdated and destructive as the Victorian ideas of keeping a lion in a 6 x 6 foot bare cage - a "lion tank", if you will. Nothing can be learned about nature from either a psychotic lion pacing around its cage or a depressed fish laying motionless in a sterile tank.
10) Although available volume must be conserved by pruning plants and occasionally scooping out sediment, microcosms never need to be "cleaned out", any more than a lake or forest floor needs to be "cleaned". Do not wage war on natural processes. NEVER "treat" tanks with chemicals in a misled attempt to reduce algal, plant or cyanobacteria growth. If you need to control a microbe bloom, simply curtail the use of supplemental nutrients, add additional filtration or increase the number of filter-feeders. Alternatively, do nothing; the bloom will eventually end naturally. They always do when some limiting resource becomes exhausted and a natural equilibrium is reached. Keep at least some of the glass clean enough for viewing by scraping off algae with a razor-blade, but don't obsess about it. Some organisms are best observed while they are attached to, or grazing on the algae-coated glass walls of the microcosm. Do not fall into the trap of thinking that reproductively successful inhabitants are "pest" organisms that must be eradicated. If a particular species is reproducing explosively, do some detective work to locate and collect it's natural predator. In some cases, population excesses can be physically harvested for use as a food source in another system. If deliberate poulation control is not practical, don't worry about it. All populations in closed systems are ultimately self-regulating.
11) Be practical. If the microcosms become too expensive or troublesome, your institution will be unwilling to support them. Whenever possible, solicit external funding and donated supplies. Use live aquarium specimens instead of expensive prepared specimens from biological supply companies. Try to make the systems a good financial investment. Learn to build and repair equipment yourself. Always keep surrounding areas clean, uncluttered and safe. Be especially careful with salt water around electricity. Make it your objective to spill as little water as possible and clean up spills and leaks immediately. Do not wait for the janitor to do it for you, by that time, the water will be coming through the ceiling of the basement.
12) Don't take much notice of what pet stores tell you is, or is not, desirable in an aquarium. Pet store staff are not professional biologists. Their main objective is to sell you relatively rare, overpriced specimens and overpriced "restaurant display" equipment, designed to allow a few, large, confused fish to drift around an unnatural fish tank, in full view, behaving unnaturally, wishing they were elsewhere. We want our students to learn how to find living things as they actually would be in the wild: hunting, evading observation, breeding and generally acting like animals do in their permanent home.
13) Strive to perpetually improve and upgrade all the displays. You will find that by constantly devising and testing your own improvements you will come to understand each system better. Some "improvements" will teach you by subsequently turning out to be a disaster. Like Lewis Carol's red queen, who ran as fast as she could to stay in the same place, you may find that a conscious effort to always improve the mechanics of each system will offset what would otherwise be a slow decline as pumps wear out, filters and pipes clog, and bulbs grow dim with age.
14) Be well read in aquarium science, specimen taxonomy and the principles of ecology, especially the following: food webs and energy flow, pyramids of numbers and mass, succession, nitrogen and carbon cycles, typical water chemistry, niche partitioning, island biogeography, factors effecting productivity and (possibly most important) factors affecting diversity (eg, intermediate disturbance, predation, grazing, extinction, immigration, niche diversity, isolation.) You might also like to read a little of James Lovelock's ideas on "Gaia". Although his ideas are controversial, they are certainly thought-provoking. Try to see yourself as Lovelock's "earth mother", constantly working to optimize the environmental conditions for your managed communities.
15) Be familiar with the specific inhabitants of each system. Keep students and other instructors informed as to which specimens are where and who is eating whom. Learn the identities of the various specimens using taxonomic guides, photos and correspondence with authorities in the field. Keep a photographic or video record of as many specimens as you can. Use your own and your student's observations to continuously expand your knowledge of taxonomy. Celebrate every time you cannot identify something, for it is not a failure of your knowledge but a chance to learn something new. Admit freely when you cannot answer student's questions, but always let them see you've looked for the answer. It will inspire them to find answers of their own. Draw attention to interesting events (reproduction etc.). These are easily missed by anyone not watching the tanks on a daily basis. Maintaining a close daily watch on your communities is also the best way to spot any potential problems before they become too serious. With experience, you will intuitively recognize when the behavior of your specimens indicates that something is not right.
16) Try to use the microcosms to teach "hands on". Choose species that can be removed and passed around or displayed in a separate dish or tray. Try to be (unobtrusively) available to direct students and instructors towards relevant species and events during classes. Don't be over-protective of the systems The students should have free and unfettered access to the tanks. Encourage the students to get their noses against the glass and their hands in the water. The microcosms are specifically designed to recover quickly and even benefit from mild disturbance. Make sure students work primarily with a microscope or magnifying lens since most species are too small to see clearly using the naked eye. Use video-microscopy and technology-based demonstrations as often as possible to help inexperienced students see what they are looking for.Encourage learning by inquiry as this will teach students how to look at any living thing, not just those in the text.
17) Try to involve students in the upkeep and maintenance of the aquaria. Offer credit for special projects or investigations. Take groups of students on collecting trips to local ponds, or rivers. I've taken several groups of students on collecting trips to Florida where they learned more about animal diversity than anything else they've done.
18) Enthusiastically promote the aquaria and remind faculty that they are available, otherwise they tend to forget and order expensive specimens that the aquaria could supply for free. Bring visitors to see the aquaria. They always enjoy seeing unusual beasties and may discover that they have a need for them in a class or project. Visitors often arrive quite spontaneously to see the tanks. Take time to introduce yourself and answer any questions they might have. By maximizing positive publicity, you may find that you will receive a steady flow of useful donated specimens and equipment that will enhance the educational facilities of the department. (Be careful ! Don't add anything too disruptive ! Watch new specimens especially closely to make sure they are fitting into the community peacefully.)
19) Remember - these tanks are different from those of a hobbyist in that they are permanent and they are for the education of professional biologists. You must insure that they remain healthy in the long term as well as the short term. You must plan your systems accordingly to reduce long term maintenance and maximize long term economy and educational value. Total redesign of a system to eradicate a problem is sometimes more economical that piecemeal tweaking or temporary adjustments.
20) If you are ever in any doubt as to the value of the tanks, just ask the students. In evaluations, students consistently describe access to diverse living aquarium specimens as a very positive aid to learning. If they don't, chances are you didn't adequately introduce them to the specimens and you may have missed the ONLY opportunity to show students live specimens during their degree course. They may live their whole life without ever seeing animals as anything other than "gross", and biological diversity will have no meaning or value to them, ultimately to the detriment of the environment.
"Filtration" and oxygenation: Almost everyone knows that keeping things alive in an aquarium usually involves mechanical devices to promote "filtration" and oxygenation of the water. What does this mean? Why do the little pond on west campus (just off the bike trail) and the fresh water tank in room 121 (F1) apparently have neither type of device? The answer to this question is central to understanding what a microcosm is. I feel obliged to beat the reader over the head with my response until you are sorry I asked the question in the first place. It is an unfortunate accident that the word "filtration" is even used in aquarium science. Perhaps a better word or phrase should be found. I would prefer "detoxoification" "chemical cycle enhancement" or "waste product / raw material concentration optimumization". Since all of these are a bit wordy you will just have to remember what I really mean when I say "filtration" from now on.
Let me start by saying what I feel filtration should NOT be in this context. A common misconception is that aquarium filters are necessary to physically strain particles and "algae" from the water like a sort of sieve. Supposedly this keeps the water "clean" so that observers can clearly see the only thing most of them care about - the fish. This defines an important difference between the objectives of a fish tank versus the objectives of a microcosm. A microcosm engineer should not strive to remove microbes from the water. Any particles which are not alive will eventually fall to the bottom as sediment and the remainder are perhaps the most important part of the system and MUST be kept in place if the microcosm is to resemble the real world. Fine grain filters do not just accumulate non-living particles, they accumulate microscopic life, and life is not a hindrance but a resource. The real purpose of "filtration" has to do with the relationship between living things and the laws of thermodynamics.
The first law of thermodynamics says that energy cannot be created or destroyed, it merely changes form or is transferred from one place to another.
The second law of thermodynamics says that without an external energy source, things tend to move towards a state of disorder or entropy. It also dictates that processes involving the transfer of energy (for example, the activities of living things) are never 100% efficient, that is, waste products of some sort are always produced and some energy is lost during the transfer process.
I will define filtration as "the input of energy to, or the exchange of materials with, an otherwise closed biological habitat in order to overcome the consequences of metabolism and the second law of thermodynamics". Filtration provides the energy necessary to keep the environment in a steady-state condition, despite the metabolic activities of, and waste products produced by the inhabitants. This very broad definition allows me to lump together a range of different mechanical devices and strategies. Most are designed to extract "undesirable" material from the water, and encourage "desirable" solutes like oxygen.
Many materials are produced as waste by living things. In fact nature's staggering biochemical diversity is readily apparent when we look at the complex soup of discarded material present in even a simple ecosystem. The most common animal wastes are carbon-dioxide gas and nitrogenous compounds like urea, ammonia and amino acids. As if this is not enough, the action of plants algae, decomposers and myriad aerobic and anaerobic bacteria may contribute nitrite, nitrate and phosphate ions, gasses like nitrogen, hydrogen, methane and hydrogen-sulfide, and organic material such as sugars, lipids, pigments, and various complex aromatic compounds. We might also find substances used by organisms to chemically communicate with each other (pheromones) and some really nasty substances used by plants to wage war on one another (a process called alleleopathy). All these substances are toxic in varying degrees to different species and should not be allowed to accumulate. It makes you wonder how living things survive at all in natural ecosystems, with all that toxic waste being constantly produced. The answer of course is that in nature, organisms have arranged themselves in complex webs, such that the waste products of one species are used as an energy source by another. The best known example of this is the relationship between plants and animals. Animals consume complex organic molecules and oxygen, then release carbon-dioxide as a waste product (this is called respiration). Illuminated plants, on the other hand, build complex organic molecules and in the process, exhibit a net production of oxygen and a net consumption of carbon-dioxide (this is called photosynthesis). So it is in countless exquisitely balanced relationships among living things. The biochemically diverse and ubiquitous bacteria of wetlands, bogs, oceans and soils are especially important in this role. There is almost no biologically derived molecule that cannot be utilized by some obscure species somewhere as a food source. The small remainder of materials that cannot be consumed are either carried away and broken down by natural physical processes or are eventually joined to or encapsulated by insoluble compounds that drop to the bottom of lakes and oceans as sediment.
The most important energy source that drives this complex natural filtration process in nature is the sun. The sun provides heat and light, which in turn generate weather, water currents, photosynthesis, and generally combat the horrible inexorable creep towards disorder and simplicity, mandated by the second law of thermodynamics. Thus, our biosphere has the amazing ability to remain complex over time and filter itself ie, it is a self-sustaining, steady-state system consisting of a perpetual cycle of materials, powered by the nuclear reactions occuring in our closest star. In the microcosm, energy from the sun is replaced by electricity to drive pumps or artificial lights, and perhaps a little man-power to establish and repair the system if necessary.
The goal of aquarium hobbyists is to replicate processes that occur in nature so that aquaria can cycle or remove toxic materials and exist in, or near a steady state, just like the real world. Modern aquarium science has devised several different types of filtration that you might come across, each with its own applications, advantages and disadvantages. The following is a general description of some of the most commonly used types, along with some notes on their application to the particular systems used by Ohio State.
Simple aeration: Also called oxygenation. The simplest form of filtration is the use of one or more air pumps to force a stream of air bubbles into the water. Usually the air line is attached to an "air stone" or other "diffuser" to increase the number of small bubbles (which dissolve faster and move water around well because they have greater total surface area than a few large bubbles.) The oxygen in the air dissolves in the water and helps the animals respire. The rising stream of bubbles is also considered beneficial because it brings water carrying carbon-dioxide to the surface where it can diffuse (or gas off) into the atmosphere. Moving the water also prevents stratification into stationary layers, the lowest of which can become depleted of oxygen. Aeration encourages bacteria throughout the tank to metabolize unwanted materials dissolved in the water aerobically, without the production of toxic gasses like hydrogen-sulfide (H2S) and methane (CH4). These waste products are characteristically produced by anaerobic bacteria and are fatal to most animals if allowed to accumulate. hydrogen-sulfide has the unmistakable smell of bad eggs and even the slightest trace of this foul odor coming from a microcosm is a sure sign of anaerobic conditions. Take appropriate action immediately. By itself, simple aeration of the water in a tank devoid of plant life or other filtration is totally inadequate for the long-term maintenance of all but the toughest specimens. It does not sufficiently encourage the conversion of toxic nitrogenous wastes into non-toxic forms and does nothing to remove accumulating nitrate and other undesirable solutes from the water. Simple aeration is also unsatisfactory because the bursting bubbles at the surface of the water increase the rate of evaporation from a tank, and because air pumps (especially cheap diaphragm types) are unreliable and wear out quickly. Perhaps the most important use of simple aeration is the maintenance of animals in temporary holding tanks, where the addition of an air pump can often mean the difference between life and death. Any time a specimen is removed from a tank and placed in a separate container you MUST add an air pump. Most organisms kept in still water with no aeration can use up all the oxygen and suffocate within minutes. Bare this in mind whenever you put a specimen in a jar for detailed observation by students.
When oxygen is removed from water it is said to be "anoxic". If the filtration of any tank is interrupted (for example, during a power failure), the water can become anoxic very quickly, starting at the bottom of the tank. Anoxia is usually accompanied by a strong smell of bad eggs. Battery powered "bait store" air pumps are indispensable during such emergencies - always keep some handy. Many marine invertebrates are especially sensitive to anoxia in still water since they have simple respiratory apparatus that depend on the constant flow of oxygenated water. Anoxia can be caused by failure to circulate water adequately, over-heating, over-feeding, or failure to remove a dead specimen (to name a few). Any of these can turn water into a nutrient-laden soup and cause a bloom (microbial population explosion) of oxygen-consuming organisms (usually bacteria) that will turn the aquarium water cloudy white or brown in just a few hours. A bacterial bloom will suck any remaining oxygen out of the water and suffocate the inhabitants.
Simple aeration is not necessary in most of our systems because of the wide variety of alternate sources of oxygenation. Trickle filters, protein skimmers, surface action and mixing caused by power-heads, simple diffusion (where volume: surface are ratio is low) and photosynthesis by plants and algae all contribute to dissolved oxygen levels.
A fish tank containing animals but no plants or filtration other than an air pump will allow the accumulation of solutes that will inevitably lead to mortality, some sort of microbial bloom or both. On the other hand a "sick" microcosm starting to look or smell anoxic can sometimes be jump-started back to a healthy equilibrium if an auxiliary, temporary air pump is speedily deployed. In this case, increased oxygen allows the inhabitants themselves (especially plants and algae) to convert or absorb the solutes that would otherwise accumulate.
The only real advantages to air pump use is that they can be quickly deployed in an emergency and they do not disrupt the all-important pelagic microbe species.
At present , simple aeration is used by itself only occasionally to boost the oxygen levels in some of our filterless freshwater tanks, particularly if they start to show obvious signs of anoxia (eg bad smell or oily film on water surface). Note that these tanks contain only invertebrate specimens that would normally live in "poor quality" water, ie stagnant pools, drainage ditches etc.
We also use simple aeration in conjunction with other filters in TM4. This system is designed to have a high content of pelagic microbes. The air stream is useful for gently mixing the water without damaging the microscopic inhabitants.
Any time a specimen is removed from a tank and placed in a separate container you MUST add an air pump.
The most common reason for air pump failure is a worn or cracked rubber diaphragm. It is usually fairly easy to take the pump apart and replace this. Replacement diaphragms are available at most pet stores.
The brown "tetra luft" air pump used on the protein skimmer of room TM1 is the only reliable brand of air pump we have found. It costs more but it's worth it.
Always use air pumps with a one-way valve in the air line and keep them higher than the tanks they are aerating. This prevents back-flow or "back-siphoning"of water into the pump (which will ruin it).
Power heads are a more powerful and reliable way to move water than air pumps.
Mechanical filtration: Earlier, I almost completely excluded this from my working definition of "filtration". I still feel that this is to be avoided in a microcosm, but I will describe it here anyway since you will probably come across it. The idea here is to use some kind of simple sieve to strain suspended particles from the water. This is traditionally considered useful mainly for keeping aquarium water clear and free of any kind of plankton that interferes with the viewing of fish. The sieve might consist of a nylon floss, a piece of sponge, or a bed of gravel sand or diatomaceous earth. Mechanical filters are quite commonly used, especially in association with other types of equipment that need to be protected from the hazard of sucking up solid lumps of gravel, plants or animal specimens. Most mechanical filters must be replaced or cleaned often because they become clogged quite quickly, either by filtered material, or by a mat of growing algae and bacteria. This constant cycle of clogging and cleaning gets annoying very quickly.
My view is that mechanical filters are best used for "fish tanks" and are undesirable in our ecosystem tanks. I try never to use them and remove them, if present, from any new pumps that I buy. Mechanical filtration removes valuable plankton and potential food particles from the water column. It reduces diversity and starves filter feeders. Mechanical filters generate a lot of work because they need to be cleaned often and they can drastically reduce the efficiency of pumps that they are attached to.
Pet stores always try to encourage you to use them because they think that you don't want a lot of algae and "bugs" swimming around in your tank (actually, we do) and because they want you to buy an endless supply of filter material.
Large national aquaria often use enormous mechanical filters filled with diatomaceous earth (a type of fine, chemically inert sand) to allow the public to see expensive specimens without the hindrance of water-borne plankton or sediment, which certainly seems to make sense in this particular case. These filters are periodically "back-washed" by passing pressurized water through them in the opposite direction and dumping the sediment laden outflow.
Some mechanical filtration may be an unintentional but inevitable consequence of other aquarium equipment like biological filters and the important "fish excluding" screens that must be placed over pump inlets. I consider this small amount of mechanical filtration to be undesirable but necessary. Only experience will tell you whether the mechanical filtration caused by a particular piece of equipment is more harmful to the system than the benefits of the equipment.
In practice, some commercial filters perceived as exclusively mechanical are actually also biological filters (see below) since bacteria will always tend to grow on the surface of the filter material. The true role of commercial aquarium filters is therefore often misunderstood by the casual observer, who may believe that the filter material should be constantly replaced as "dirt" accumulates on it . In reality the filter should be left alone for as long as possible to carry out the much more important function of biological processing.
Sponges tend to clog especially quickly (even the coarse ones) and its a pain in the neck to keep cleaning them. I have learned to avoid them. Almost all commercial water pumps come with these. I remove them. This has never caused me any problems, but be sure that there is no danger of specimens being sucked into the pump. Attaching the intake to a coarse-mesh screen or coarse-grained under-gravel filter is often a better, low maintenance way to exclude specimens from pumps.
The algal scrubber (described under "natural filtration") is claimed to be one of the few types of filtration which does not also mechanically strain living organisms out of the water column. It therefore seems ideal for microcosm use. Unfortunately most types of centrifugal pump used to send water through the scrubber still tend to kill water-borne microbes, so ultimately the algal scrubber is prone to the same major draw-back as any other type of filtration.
Adey's lab and others are experimenting with non-destructive pumps such as the Archimedes screw and slow moving piston pumps as a way to move water around without stripping it of its microbe inhabitants. I think that anyone who can come up with a cheap, compact, reliable way to pump water around a hobyists aquarium without striping it of its microfauna would make a lot of money.
The only natural process that might be considered a possible counterpart to mechanical filtration is sedimentation. Sedimentation keeps water free of suspended particles by allowing them to sink to the bottom and accumulate as sediment.
Removal of sediment from our microcosms is analogous to the use of mechanical filtration in that the objective is to remove inert particles. The advantage of waiting until these particles sink is that this prevents loss of beneficial plankton. The Smithsonian microcosms have tried to include settling areas intended to automatically concentrate sediment near an outlet valve so that it can be easily disposed of. I observed first hand that these are not very effective because it is surprizingly hard to predict exactly where sediment is most likely to be deposited. It may eventually be possible to design some sort of effective sediment trap for use with our systems, but for now, physically removing observable accumulations of sediment using a vacuum tool or scoop seems to be our only option.
In freshwater systems, the two tiny, aquatic angiosperms Lemna and Wolfia can and spread very rapidly. I use a fine net to physically harvest the plants from the water surface for composting. I suppose this constitutes a form of mechanical filtration.
Similarly on the rare occasions that I perform water changes on the small fresh water systems, I usually strain the old water through a net to retain as much plankton as possible.
Chemical filtration: This refers to the use of special chemical absorbents to extract undesirable solutes from the water. Typically, a nylon bag (never cotton - it rots) is filled with activated charcoal, then placed in some sort of container through which aquarium water flows. Alternatively, special chemical absorbents can be purchased from most pet stores. Examples include "bio chem zorb" (which comes ready to use in nylon bag and "polyfilter" (which comes as a square of white absorbent mesh, which can be cut or rolled to size before being placed directly in the path of the water). Toxic solutes are preferentially bound and held by the absorbent, leaving the purified water to flow back to the aquarium. This technique is very effective and has a wide range of applications including the pre-filtering of tap water to remove chlorine, copper and lead. Only filtered or otherwise purified tap water can be used in the marine microcosms. Chemical filtration is the ONLY practical way to remove some kinds of toxins (other than a full water-change) and is therefore very important. Modern chemical absorbents have been developed for aquaria that can suck a variety of accumulating toxins out of the water including ammonia, nitrates and phosphates, but this technique is especially useful for removing heavy metals, proteins and other soluble organic material. A clear yellow or brown hue to the water, or declining pH usually indicates the build up of dissolved organic material, and is a sign that you may need to add (or replace) a charcoal filter.
Removal of dissolved organic material raises the levels of dissolved oxygen and the oxygen potential of the water. The oxygen potential of a marine aquarium is a function of several variables, and is generally considered a good measure of the aquarium's ability to hold dissolved oxygen and overall water quality. Unfortunately oxygen potential can only be measured using a special oxygen electrode and meter that the department does not own at the time of writing.
The main disadvantages of chemical filtration are as follows: a) Chemical absorbents are very expensive, far too expensive to use exclusively in all of our tanks all of the time. b) They become exhausted quite quickly and have to be replaced. c) They may mechanically filter valuable plankton from the water column and their effectiveness may be reduced by mechanical clogging and growth of bacteria on the filter material. d) No single type of absorbent can remove all toxins. Few can remove salts (from freshwater tanks), most cannot remove phosphate and nitrate (unless specifically made for that purpose.)
Activated charcoal can usually be obtained free from a Columbus company, Barnaby-Sutcliff Co. (if you ask the manager nicely) or it can be purchased in bulk inexpensively from Wards. Use either continuously, or to occasionally supplement other forms of filtration, especially if the water in a tank begins to acquire the characteristic yellowish hue. Charcoal is not the most efficient chemical absorbent, but it is the cheapest. I also sparingly use commercial absorbents in the marine tanks when the budget will allow.
New chemical absorbents are appearing on the market all the time. feel free to experiment with new brands.
Chemical filtration is great for providing clean water when distilled water is unavailable. I usually pack a PVC cylinder with a round piece of polyfilter cut to sit at the bottom of the cylinder and a bag of charcoal on top, then very slowly trickle water through the cylinder and collect the eluate. I usually filter a large amount of water at once (50 - 100 gallons usually lasts me a couple of weeks) then I unpack the cylinder and immediately use the absorbent elsewhere (for example in a power-filter chamber.) I don't leave the packed cylinder sitting around as it can absorb material from the atmosphere, reducing it's future effectiveness.
Another technique is to fill a 1" diameter clear PVC hose with a few tablespoons of bio chem zorb using a funnel, plug the downstream end with a small piece of polyfilter or nylon floss, then ring-clamp some nylon mesh over the end to hold the material in place under pressure. The other end is mated to a faucet or hose pipe. Turn the water supply on to a very slow trickle, allow any charcoal dust to emerge then collect the outflow once it starts to run clear. This can yield up to a hundred gallons of water before the filter material needs to be changed.
When filtering tap water from a running faucet, don't leave the set -up unattended; its an easy way to have a flood. Even a very slow trickle can make a hell of a mess if it runs onto the floor for just a few minutes !
Be sure to rinse bags of filter material well before you use them; they initially produce a large amount of loose black dust that you don't want to introduce into the tanks.
You can remove and rinse bags of filter material that are "in use" to remove accumulated debris then return the bag to the system.
Most chemical absorbents have a maximum useful life of about 6-12 weeks, or 1- 2 weeks for charcoal.
Charcoals vary greatly in their efficiency, "lab grade" charcoals are usually the best.
Regenerative absorbents for aquaria have recently appeared on the market that can be treated with acids or bleach to reactivate them so that they can be used again and again. I haven't tried them yet but I suspect they might be too much work for use in our systems. They are also quite expensive but their price may drop as their popularity increases. Feel free to give them a try.
Chemical filtration is most important to the marine tanks - freshwater organisms tend to be quite hardy and pollution resistant. I only use chemical filtration in freshwater tanks if the water is visibly discolored. For economy it's best to cut open a bag of "bio chem zorb" and use only a couple of table-spoons at a time in a smaller bag tied closed with a knot.
If ozone is used in any tank, most aquarists usually recommend that the water flowing out of the ozone chamber be passed through a bed of charcoal before it returns to any other part of the system. This ensures that any active ozone is absorbed from the water before it can burn your specimens.
I use a small bag of charcoal in the protein skimmer outlet canister of TM1, which I change every two weeks. Note that the bag hangs in place by fitting the sealing knot into a small notch on the canister. Note also that the bag has been perforated to reduce clogging. I use a commercial absorbent like polyfilter in the siphon box of TM1, which I change once every three months or as needed. I also use absorbents in the other tanks if the water in them begins to look yellow. I have found "polyfilter" particularly effective when inserted into the external filter box of a power-filter, and reasonably economic if it is cut into 2"X1" pieces that fit snugly into the box. Use each small piece until it turns very dark yellow or brown.
I use a small bag of charcoal in the downstream arm of the U shaped protein skimmer in the cold water marine tank (CM1). I change this every month.
With a bit of thought, you can devise a temporary, auxiliary chemical filter for occasional or emergency use with any tank, or for filtering tap water (see diagram). I recommend that you do not leave auxiliary filters unattended or a flood may result.
One of my favorite ways to combine filtration techniques is to use a "power-filter" modified to drive a combined under-gravel / chemical absorbent system. This neat little set-up is very effective. Simply drop a small bag of absorbent or a 3x3 inch square of polyfilter in the power-filter chamber. Just one of these work-horse filters can take care of filtration in a freshwater tank of up to 40 gallons (depending on the biological load).
Protein skimmers: These devices are used to separate out organic material from aquarium water. They are also known as foam fractionators. They typically consist of an upright tube filled with water through which a mist of fine air bubbles is passed. Organic materials tend to accumulate on the surface of the air bubbles as they pass through the water column, just as oil tends to accumulate on the surface of water. When the bubbles reach the surface they burst and leave behind their film of organic material. As the organic material accumulates, it begins to form a foam which builds up at the surface of the skimmer. This foam can be scooped off or collected in a small container, then discarded. Air bubbles are introduced into the column by either an air pump, a "venturi valve" (a special needle valve that allows a stream of fast moving water to draw tiny air bubbles into the stream) or by mixing air and water in a power- head prior to its injection into the column (see TM 4 and CM). Typically air bubbles are injected into the lower part of the column and then rise to the surface. At the same time water travels from the top of the column to an exit point at the bottom. This counter-current setup allows air bubbles to contact a large volume of water during their journey, collecting as much organic material as possible and oxygenating the water thoroughly. The efficiency of the protein skimmer improves with increasing size, total volume of injected air, decreasing average bubble size, and optimization of water flow rate through the column.
The function of the protein skimmer can be improved (actually, completely transformed) by introducing ozone gas to the column. Ozone (O3) is used industrially as a bleach and sterilizer. It is a highly reactive gas that can be made by an electric arc between two electrodes in air. Ozone occurs naturally as a result of lightning discharges and the action of UV light in the upper atmosphere. It is very soluble in water and rapidly converts to O2 and an oxygen free radical. The free radical reacts with almost any large organic molecule (or molecule complex) breaking it down into smaller units. Ozone is a powerful oxidant and care should be taken not to inhale large quantities or allow it to leave the skimmer unit. If it enters the microcosm it may injure specimens, or destroy the bacteria responsible for biological filtration.
The two best ways to prevent unwanted ozone "burn" where you don't want it is to use a little activated charcoal to filter the water that leaves the column. I have found ozone very effective at maintaining clear, clean water in the large tropical marine system in rm 121 and strongly recommend it's use.
Once large organic molecules have been "cracked" apart by ozone they are more easily metabolized by bacteria and removed from the water. You will notice that very little foam will be produced in a protein skimmer using ozone because most of the organic material that normally produces the foam is "burned up" (oxidized).
Protein skimmers reduce the amount of organic material in the water and help to raise the levels of dissolved oxygen and the oxygen potential of the water. The oxygen potential of a marine aquarium is a function of several variables, and is generally considered a good measure of the aquarium's ability to hold dissolved oxygen and of its overall water quality. (It can, however, only be measured using a special oxygen electrode and meter that the department does not own at the time of writing.)
Some marine aquarists use a huge, powerful protein skimmer as the only filtration device on their tanks. This is sometimes called the Berlin method because it was first popularized in Germany.
One important disadvantage of using protein skimmers, particularly if you use ozone is that they usually kill waterborne plankton. You can try to minimize this loss by allowing only a very slow flow of water through the device. If the inflow rate is slow enough, many plankters will avoid the inlet port by swimming away.
Protein skimmers may be used with marine or freshwater aquaria, but are more common in the former, who's properties tend to cause quite a rapid accumulation of dissolved organic material. Ozone is only rarely used with freshwater tanks, typically only where there is an unusually large biological load.
Ideally, the water entering a protein skimmer should be drawn from the surface of the system since that's where most of the organic material accumulates.
Use of a protein skimmer with or without ozone may lead to the accelerated loss of trace elements from the system. Be sure to replace these by adding commercial trace elements. This is especially important for the marine tanks.
Ozone machines need to be attached to an air pump. Air moves through the ozonizer, some of it is converted to ozone, then the air and ozone move to the skimmer.
Use only ozone resistant silicon air lines between the air pump and the skimmer. PVC is attacked by ozone. Most pet stores sell both types.
The part inside the ozone machine that produces the ozone (the lamp) wears out eventually and will need to be replaced. You can tell when this happens because the fractionator starts to produce more foam and the aquarium water may begin to turn yellow.
Keep the air pump and ozone machine well above the height of the skimmer and tank water level, and use a one-way valve in the air line, or I promise you that eventually water will seep downwards or back-siphon into the ozone machine causing a spectacular but dangerous electrical short. This is most likely to be caused by a brief power failure or when the air pump diaphragm wears out. Note that the ozone machine attached to TM 1 is raised above the level of the tank and MUST be kept in this raised position. If water gets into the ozone machine it is ruined.
If you can smell ozone there may be a problem. Check the skimmer and air lines.
In protein skimmers that use air diffusers, keep an eye on the amount of air that is entering the column. If it looks like not much air is entering, the diffuser may need to be cleaned. I have found that air stones clog very quickly in skimmers so I try to avoid using them.
Since we have only one ozone machine at present (attached to the TM 1, 2 , 3 system) I find it useful to exchange some water between TM 4 and TM 1 weekly so that the water in TM 4 stays fairly clear. The small hole in the wall separating rm. 129 and rm. 121 (under the sink) may help you pump water between rooms.
Look inside the TM1 skimmer often to check for air bubbles and correct water level (level should be same as TM1). If no air is bubbling through the skimmer, either the air pump is not working properly (the rubber diaphragm probably needs to be replaced), or the silicon air line is clogged, punctured or disconnected. Check the inflow and outflow pipes often to make sure that they are not clogged. The inflow pipe is a self-regulating siphon. A clamp on the ouflow pipe allows the outflow rate to be adjusted. It should be set to approximately equal to the inflow rate. Outfllow rate is optimum when it is as fast as possible but still allows the skimmer's internal water level to remain approximately equal to that of TM1.
We added a power head with an inverted funnel to the TM1 skimmer. This allows us to do away with the annoying, frequently clogged air stone because the large bubbles released at the bottom of the skimmer are now caught and sucked into the power head, then blasted out as a fine mist.
The protein skimmer for CM1 sits inside the tank in order to conserve thermal energy (ie. to avoid heat gain from the surroundings). Ozone from room 121 is pumped to both TM1 and CM1 using a system of branching airlines. One of these runs through a hole in the wall and injects a little ozone into the power head associated with the CM1 skimmer. Make sure you change the charcoal in the CM1 skimmer often.
Circulation and surface skimming: Note that many filtration devices depend on the action of a pump (or pumps) to move water through the equipment. The pump itself is valuable because it provides circulation of water. Circulation of water helps to keep aquaria well oxygenated by moving water to the surface of the tank where it can absorb oxygen from the air and release (or gas off) carbon-dioxide and other dissolved gasses. Circulation prevents stratification and the formation of still areas or dead spots where anoxia may occur. Adequate circulation is especially important in marine tanks, since some marine invertebrates rely on rapidly moving water for both respiration and feeding.
The most common way to move water is with one or more centrifugal pumps. These rely on a spinning set of paddles called an impeller. Small submersible versions with directable nozzles are called power heads. Larger submersible models that sit in a box (or sump) under a system are called sump pumps. Other types like the main pump in CM1 run dry, that is, only the impeller touches water, the motor must be kept dry. The most common causes of failure are jamming due to sucking in some kind of obstruction, and overheating, especially if a pump designed to run under-water is run dry.
Power heads can be used by themselves to generate circulation in any tank. Most of them come with a mounting bracket that lets you position them as needed. Typically they are placed somewhere near the surface so that the flow of water out of the pump generates lots of ripples or surface action, which is considered desirable because it helps to mix oxygen in with the water and breaks up the surface film of organic material that can accumulate on the water surface. This film is analogous to a layer of oil floating on water and can act like a barrier to the movement of oxygen. The film is visible on the surface of most tanks if you look carefully, especially from underneath, and can be a big problem in the tropical marine tanks, which tend to accumulate the film very quickly. The problem can be countered by skimming the surface of the water to remove the film. The siphon box in TM1, the position of the outlet tubes in TM2 and TM3, the inverted power head and side drain boxes in CM1, are all examples of ways to skim off the surface film of organic material. Ideally, surface skimmed water from a marine tank should flow directly to a protein skimmer or chemical filter to remove the organic material. In fresh water tanks, good surface action is normally adequate to mix in the surface film with the rest of the water so that it can be broken down or absorbed by the filter system. Surface film accumulation rarely if ever seems to become problematic in our fresh water microcosms, even though I have frequently observed it on the surface of hobyist's fish tanks.
A related piece of trivia - the guppies in the fresh water tanks have been seen eating the surface film. It may be an important food source for them. Perhaps that's why it doesn't accumulate in these tanks.
Most of ours power heads were donated by Aquarium Systems Inc. (Mentor, Ohio). All it normally takes is a polite letter asking for one. Manufacturers are also usually quite happy to send replacement parts free of charge.
Variation in the circulation pattern that mimics natural wave action seems to be important to the growth of some marine organisms. Accordingly we have connected some of our pumps to electrical boxes that act as wave generators. These can be programmed to turn pumps on and off in such a way as to mimic waves or tides. Be sure that alternation of power-heads attached to the same under-gravel filter does not allow a "short circuit" of water from one pump to the other without passing through the gravel. Another type of wave generator comprises an axle-mounted box that fills slowly then dumps its contents all at once when the center of gravity changes. A third type is the self-establishing siphon box that fills until the water level reaches the top of a specially shaped outlet tube which then forms a siphon and rapidly empties the entire box until the siphon breaks.
Power heads are versatile and reliable but do need to be taken apart and cleaned once in a while. Be particularly careful to keep the water path (intake, outlet, and all associated tubing) clear of accumulating material. Even a small build up of organic material on the inside of tubes causes drag that can reduce flow significantly.
Power heads overheat and seize if they run dry (ie unsubmerged). Due to design error we have a couple that operate like this (the bog tanks). Cooling of the pumps in these systems MUST be maintained by directing a steady trickle of water over the unsubmerged pump.
Power heads create considerable suction at the intake end. If their is no protective screen or other excluding device, it is certain that sooner or later specimens will get sucked in and minced.
Power heads can be used to oxygenate water by mixing fine air bubbles with the water leaving the pump. Some power heads are designed to do this using Bernoulli's principle; a small hole in the outlet nozzle allows the air to flow from the surface, through a short air line and into the fast moving water stream. Alternatively, if air is introduced near the inlet port it will be sucked into the pump, broken into tiny bubbles and blasted out as a fine mist. This technique is used in the protein skimmers associated with TM1 and CM1
Without any doubt, the best submersible sump pumps are made by Ehiem. These require only occasional dismantling and cleaning. They run problem free seemingly forever.
Keep pipes clean using the pull-through tool that is actually a length of thick, stiff nylon monofilament with a hook on one end to which a small wad of floss can be attached. All pipes in the tropical marine system should be cleaned 3 or 4 times a year.
Unfortunately the high pressure and mechanical sheer forces generated by most types of centrifugal pump tend to kill water-borne microbes. This is a serious disadvantage to the use of power heads in microcosms.
Adey's lab and others are experimenting with non-destructive pumps such as the Archimedes screw and slow moving piston pumps as a way to move water around without stripping it of its microbe inhabitants. I think that anyone who can come up with a cheap, compact, reliable way to pump water around a hobyist's aquarium without striping it of its microfauna would make a lot of money.
A gentle stream of bubbles from an air pump can be used to move water around a tank without damaging suspended microbes but this technique has several limitations: Cheap air pumps wear out quickly , air stones or diffusers often clog, a stream of bubbles at the surface massively increases evaporation and finally, water cannot easily be lifted to any significant height above the system by air pumps.
Note that "Stagnant" means still. A stagnant pool is usually considred unclean because it is likely to be anoxic and may therefore may smell of hydrogen sulfide and be devoid of any visible life. This is especially likely if the light intensity, plant density and photosynthesis are low, or if the temperature or biological load are high. Our microcosms are lucky enough to sit in a well lit, temperature regulated room so even though some are technically stagnant, natural filtration (discussed below) is often enough to prevent them from becoming anoxic. Because of the natural filtration and oxygenation, mechanical circulation is not always necessary in a microcosm, although it is almost always essential in a fish tank.
Biological filtration: This is perhaps the most important type of filtration that goes on in any tank because it is effective, free, and deals with the most important and potentially troublesome solutes that are certain to be in any tank containing animals. One might expect the term "biological filtration" to include the whole range of metabolic activities carried out by all the organisms of the community. In reality, it has become a standard aquarium convention that the term specifically and exclusively refers to the action of certain aerobic bacteria involved in the aquarium's nitrogen cycle. By convention, I will call other types of filtration performed by any organism other than the bacteria of the nitrogen cycle "natural filtration" and deal with it separately later.
Animals produce nitrogenous waste products as a result of their metabolic activities. Many aquatic organisms release these as the highly toxic compounds ammonia and / or urea. The amount of ammonia and other nitrogenous waste products released into the water is a function of the "biological load". This is basically the total mass of animal specimens in the tank, although it may be affected by other factors like individual metabolic rates, specimen size, diet, amount and type of substrate, temperature, mass of live and decaying plant material, and disruptions to the system like cleaning or equipment failure. Generally, as the biological load in a tank increases, so does the rate of accumulation of nitrogenous waste products in the water. These toxic substances must be either removed, or converted into other less toxic substances. The urgency of this task varies somewhat with the type of specimens kept in a given tank - some freshwater fish are moderately tolerant of nitrogenous pollutants, marine fish and inverts are much less tolerant; they tend to go "belly-up" particularly quickly in the presence of relatively tiny amounts of ammonia.
Luckily, the world is filled with biochemically diverse bacteria. Some of these, under the right conditions can rapidly metabolize urea and ammonium ions and convert them to slightly less toxic nitrite ions. Other bacteria can metabolize nitrite and convert it into the relatively harmless nitrate ion. The nitrate ion (NO3-) is quite stable, but under the right conditions, it too can be broken down and (slowly) removed from the water by the action of certain bacteria, particularly anaerobes. It may also be absorbed and utilized as a nitrogen source by plants and algae. The effective biological removal of nitrate from the water requires an active and diverse assemblage of different organisms. Many traditional fish tanks are never able to reach the point where nitrate is eliminated faster than it is produced. This is quite common in tanks where there is too much animal mass and not enough plant material. I should stress that the ability to remove nitrate is another fundamental advantage of the microcosm concept over the traditional fish tank.
Some aquarists counter the gradual build up of nitrate with regular partial water changes. Others use expensive devices called denitrators to encourage the growth of partially anaerobic denitrifying bacteria. Another option is to incorporate one of the newer chemical absorbents that will remove nitrates from the system. I prefer to ALWAYS set up a tank such that it is capable of eliminating all its own nitrate. I have found the other techniques too be expensive, too much work and, most importantly, too unreliable. A tank that lowers its own nitrate levels will rarely let you down. The other techniques can fail. The best way to make sure that a tank is "self - denitrifying" is to keep it filled with rapidly growing plant material. More of this later under "natural filtration".
Biological filtration is performed by under-gravel filters, wet-dry (or "trickle" filters), "biowheels" (a gimmicky variant of the wet-dry filter), and by any available surface or substrate where bacteria grow (including gravel, porous rocks, even the surface of the pipes, pumps and the aquarium itself. )
Under-gravel filters are one of the most widely used aquarium filtration devices since they are simple and easy to maintain. When used properly they are effective at converting ammonia and urea to nitrites then nitrates, provided that they are not burdened with an excessive biological load. The idea is to allow water to percolate down through a bed of gravel. The gravel provides a large surface area for the growth of numerous bacteria that digest toxic pollutants like ammonia and urea. The gravel rests on an under-gravel plate. A lift tube allows water be sucked out from under the gravel and forced back to the surface of the tank. Most under-gravel filters were originally designed to be used with an "air-lift" system (a stream of air bubbles in the lift tube, produced by an air pump), but this technique is generally giving way to the much more effective power-head driven filters, which use a reliable centrifugal impeller pump to pull water through the gravel bed. Some people prefer to use the "reverse flow" under-gravel filter, which uses a power head to force water down a tube and then upwards through a bed of gravel. This prevents the gravel bed from becoming clogged with sediment but is otherwise probably identical in performance to the regular under-gravel filter. Note that the gravel is merely an inert surface on which bacteria grow. Make sure the gravel is well washed before use in a new tank and free of chemicals like dye or other impurities (don't use goofy colored aquarium gravel) In some cases (usually marine tanks) it might be useful to use a calcareous substrate like dolomite or crushed coral, which is slightly basic (alkaline) and will slowly dissolve, making the water more alkaline and introducing calcium. This is especially useful in tropical marine tanks, which should be kept at a slightly alkaline pH ( typically 8 - 8.4) but less desirable for most freshwater tanks, which are usually kept close to pH 7.
Trickle filters (wet / dry filters) like the one in the sump of TM1 and commercial variants like the overrated "biowheel" also use bacteria to convert ammonia and urea to nitrites then nitrates. They work by allowing aquarium water to flow over a wet (not submerged) surface on which a film of living bacteria grows. Huge trickle filters are used in many municipal water treatment plants and national aquaria as an effective way to treat and aerate large volumes of fouled water. Trickle filters have been found to be more efficient than under-gravel filters for aquarium filtration because they allow the rapid growth of highly effective, aerobic, ammonia-metabolizing bacteria in an oxygen-rich environment without clogging. This type of filter is often considered essential in marine tanks because marine invertebrates and fish are very sensitive to ammonia levels. The substrate in a wet / dry filter is used only to provide a large surface area for the growth of bacteria. Many different types of substrate are available commercially, I'm sure it really doesn't matter which one you use (despite the claims of the manufacturers.) since the substrate itself is basically inert and not involved in the filtration. There are plenty of blue - spikies and orange disks in the B&Z store room - these seem to work fine. We have also had success with the crushed reef rock in the sump of TM1. It's porous surface probably provides a wonderful home for bacteria and has the advantage of acting as a calcium source.
The biowheel is essentially a power-filter to which a rotating cylinder of porous nylon plates is added. The cylinder provides a damp, aerobic surface on which bacteria can grow, performing the exact same function as in a trickle filter. I dont like it much because the moving parts eventually clog up and stop moving. It's main advantage is that it is eay to add on to an existing system and it is quite compact.
Another variant, the fluidized substrate, (= "fluid bed" or "fluid phase") filter uses a container filled with small inert particles (often glass or plastic beads). These are kept in constant motion like a swarm of densely packed, angry bees. Water is passed over them, usually from the bottom up. The idea is that since the entire surface of each bead is available and surrounded by highly turbulent aerobic water, bacteria grow very quickly but are often displaced by collisions, freeing up real estate for new bacteria to grow on. As a way of dealing with nitrogenous waste, this technique is very effective but seems like overkill to me, since I can find no trace of nitrogenous compounds in our systems that use only a simple trickle filter.
Remember that the bacteria that live in under-gravel and trickle filters do not appear instantaneously. When you set up a new tank you will have to let it run for a few days or weeks to allow bacteria to grow before you can add any animals. The death of prematurely added specimens to an unprepared tank is called "new tank syndrome". Addition of commercial, dried "starter" bacteria (eg "biozyme") and some fish food to a new tank is often a good idea to help activate the biological filter and prevent new tank syndrome. Some people also like to add the cheapest fish they can find to a new tank and watch it carefully for a week to see if it looks happy, indicating adequate water quality. This intrepid pioneer helps to innoculate the filters with bacteria and provides nitrogen for the bacteria to feed on.
If a tank becomes badly polluted (by say, a dead fish or excessive biological load) the bacteria in the filter may be overcome and killed, resulting in a dangerous logarithmic rise in ammonia or "ammonia spike".
Under-gravel filters tend to become clogged over time. This can be prevented by occasional vacuum cleaning of the gravel, or by inverting the power head that drives the filter (so that water flows opposite to its usual direction of travel, dislodging some of the clogging material), or even by simply turning the pump on and off several times each day to jolt loose enough material to keep the filter working properly.
Although an under-gravel filter with fine grade gravel has a great total surface area for the growth of bacteria, I have found that they tend to get clogged quickly. I prefer to use coarse (pea sized) gravel. Although the total surface area of coarse gravel is lower, they need less upkeep and are therefore more effective and reliable in the long run.
Make sure that water is passing through the gravel or over your trickle filter and has not found some alternate path. This might happen if, say, an undergravel plate gets lifted slightly so that water travels around and under it, then back to the pump without ever passing through the gravel bed.
Although most aquarists aim for uniform flow of water through a gravel bed, I prefer to encourage biochemical diversity by creating variation in the substrate depth, gravel size and water flow rate so that aerobic, anaerobic, high flow and low flow areas exist in the same gravel bed. This encourages the kind of microbial diversity seen in nature.
Coarse substrate, under-gravel filters often make a good pre-filter for power-heads. Their function as such in TM1 probably outweighs the value of the biological filtration provided by the gravel bed.
Natural filtration: I define this as the whole spectrum of biological recycling processes that would normally occur in a natural ecosystem. This includes the action of all aerobic and anaerobic bacteria, absorption of nutrients by angiosperms and algae, sedimentation, mineralization, photolytic reactions, the action of natural catalysts and buffers and the action of often overlooked infaunal or planktonic protists and invertebrates. These important decomposers help to consume organic material before it can cause a dangerous bloom of bacteria. Natural filtration may be assisted by the action of electrical pumps to move water around, or it may be effective without any electrical pumps at all. Like biological filtration, It is primarily involved in the nitrogen cycle, but it may also be responsible for removing a range of other organic and inorganic material from the water and be partially or fully responsible for oxygenation of the microcosm through photosynthesis.
Natural filtration is the main reason that our tanks are so much more resiliant to unconsumed organic material than a typical hobbyist's fish tank. Even quite a large, whole dead fish thrown into TM1 would quickly and harmlessly dissappear into the food chain. If the same dead fish were thrown into a conventional ornamental display it would probably cause the rapid demise of all the inhabitants.
The freshwater tank in room 121 (FW1), the leaf litter tank and the small freshwater systems on the table near the window in room 129 have no active filtration apparatus or pumps and maintain a hospitable environment for their inhabitants using only natural filtration. All of the other tanks are set up to encourage as much natural filtration as possible to supplement the action of the electrically powered filters. Remember that natural filtration is powered mainly by light (natural or artificial.) For this reason you should try to keep all your tanks as well lit as possible. (See section on lighting.)
Probably the most important of part of the natural filtration in an aquarium comes from the action of macrophytes (plants) and algae. These suck animal waste products such as nitrogen compounds and phosphates out of the water and use them as raw materials for their own growth. I have found that a tank containing a large mass of rapidly growing plant material rarely or never has a problem with excessive nitrate or phosphate levels, and never suffers from microalgal blooms (indicated by cloudy green water). ALWAYS maintain adequate lighting and lush growth of plant material in the aquaria. When you prune back and remove excess plant growth , you are actually plucking nitrogen and phosphorous compounds straight out of the system. The pruned material can be added to the leaf litter tank where it will decompose and feed the inhabitants. In some aquaria, the photosynthetic component of natural filtration can also provide for the oxygen requirements of all the animal inhabitants.
Try to encourage as many species of plant and macroalgae as possible. Not only are growing plants one of the best ways to maintain water quality - they also provide food and shelter for the animal specimens, encourage natural behavior patterns and help to generate a heterogeneous mix of micro-habitats that can hold many different species.
Another part of the natural filtering process can occur inside porous rocks, and in the partially anaerobic bed of substrate at the bottom of the tank. Some aquarium books will describe potential hazards of having any anaerobic areas in your tanks, (namely, the evolution of certain gasses like hydrogen-sulfide) and will advise you not to include any gravel substrate in tropical marine tanks (incidentally, giving your tank a bizarre, unnatural, glass-bottomed look). I have never had any problems related to production of toxic gas within anaerobic substrate and believe that this is because gasses remain either locked up in small pockets, or escape as large bubbles that move quickly to the surface and are released. Anaerobic bacteria are known to be important in all ecosystems, and reports of their ubiquity and (previously unsuspected) vast diversity and numbers are becoming more common all the time. Since they are important in nature, I would argue that they absolutely belong in our teaching aquaria. Two of the most successful closed marine ecosystem tanks in the world (the Smithsonian's in D.C and the Cousteau in Monaco) both feature deep layers of anaerobic, calcareous substrate. The staff at the Smithsonian have told me that they believe the anaerobic metabolism and CaCO3 cycle in the substrate is an important form of filtration, good for breaking down soluble nitrates, eventually releasing the liberated nitrogen from the tank as large bubbles, and increasing the dissolved calcium in the water. Since anaerobic bacteria use dissolved organic material as an energy source, the anaerobic substrate filter may also be a way of removing dissolved organic material. I have seen hobby versions of this in both fresh and marine tanks that resemble an unusually deep, reverse-flow, under-gravel filter with very fine gravel.
Natural filtration is aided by maintaining a high level of physical diversity in each tank. In other words, try to ensure that there are areas that support as many different metabolic processes as possible: aerobic and anaerobic, rocky and muddy, turbulent and less turbulent, bright and dark, wet and dry (if possible). A physically diverse tank, subdivided into different, areas, will encourage a greater variety of bioremedial processes and greater biological diversity than a homogeneous tank.
The idea of a complex aquarium maintaining itself using natural filtration better than a simple one is supported by the emerging sciences of chaos and complexity. These seem to hint at the possibility that complex systems have the ability to "self-organize" in such a way that, some sort of equilibrium will eventually be established and maintained as a result of subtle interactions between the system's components. (See "complexity" by M. Mitchell Waldrop.) By encouraging as plant, algal, animal and physical diversity in each system, you will help the inhabitants to organize into a stable energy web that will be aesthetic, robust, cheap to run and easier to maintain in the long run than a more traditional, low diversity "fish tank".
Algal scrubbers: This is really just another way to encourage natural filtration processes. Walter Adey of the Smithsonian Institute's marine systems lab in DC was the first to develop this technique for aquarium use, although variations of the basic principle have been used in other labs for years, particularly in the field of aquacultue. The idea is to use rapidly growing filamentous algae to suck nitrates, phosphates, carbon dioxide and other materials out, but force oxygen in, all with minimum possible reduction of live plankton and other potential filter food from the water colomn. The Smithsonian technique involves growing an "algal turf" on a fine mesh screen, in a shallow, wave-agitated tray. Wave motion seems to be a crucial factor in the growth of many filamentous algae. Multiple trays are usually used so that they can be lit on anti-synchronized twelve hour cycles. This insures that photosynthesis is always occuring in one of the trays, even when the tank itself is in darkness.
Some aquarium hobbyists have reported problems with yellowing water (supposedly due to leaching of algal pigments). Presumably additional filtration, such as a protein skimmer with ozone would help to remove the yellow color. Dr. Adey insists that this is not causally related to the use of the algal scrubber. If you want to know more about the algal scrubber you should consult Dr. Adey's useful book "Dynamic Aquaria".
I have often thought about building an algal scrubber for use with some of our tanks but have been prevented by time, space and economic restraints. I also wonder how useful they would be with our particular tanks, most of which could be considered to have their own algal scrubbers "built in" to the system. The use of the anti-synchronized algal scrubber trays was the inspiration for the partially anti-synchronized time cycles used to light TM1,2 and 3. The object is to dampen any chemical fluctuations in the water that might be caused by all lights going on and off at the same time.
Naturally lit algal scrubbers housed in greenhouses have also been used effectively at the Smithsonian and at the Pittsburgh Zoo.
The algal scrubber is claimed to be one of the few types of filtration which does not mechanically strain living organisms out of the water. It therefore seems ideal for microcosm use. Unfortunately most types of centrifugal pump used to send water through the scrubber still tend to kill water-borne microbes, so ultimately the algal scrubber is prone to the same major draw-back as any other type of filtration.
Adey's lab and others are experimenting with non-destructive pumps such as the Archimedes screw and slow moving piston pumps as a way to move water around without stripping it of its microbe inhabitants. I think that anyone who can come up with a cheap, compact, reliable way to pump water around a hobyists aquarium without striping it of its microfauna would make a lot of money.
Using multiple filters: This is generally useful in most situations. Some aquarium scientists have pointed out that there may be a conflict between different sorts of filtration. For example, the effectiveness of an anaerobic denitrator may be reduced by the use of a protein skimmer because anaerobic bacteria require dissolved organic material as an energy source for their activities. Although this may be true, I would still recommend the use of more than one form of filtration in all our marine tanks. Although some combinations of filtration techniques may not be especially synergistic, most are, and very few combinations are entirely antagonistic.
Remember some organisms are very sensitive to pollutants in the water and since our displays are permanent, the eventual failure of any given filter is almost guaranteed given enough time. On the other hand, the simultaneous failure of several filters at once is somewhat unlikely. This is why I try to make sure that the most sensitive marine tanks have at least two independent sources of filtration (or at the very least, 2 independent sources of circulation.)
Fresh water organisms are a little hardier, and most can survive a period of hours to a few days without a working filter, provided that there are a few well-lit plants in the tank to provide O2. An equipment failure at night is often survivable since fish tend to be inactive then, requiring little oxygen. For this reason, (and economy) most of our fresh water tanks have only a single electrical filter (if any).
One of my favorite ways to combine filtration techniques is to use a "power-filter" modified to drive a combined under-gravel / chemical absorbent system. This neat little set-up is very effective, especially if you use a good chemical absorbent like "bio chem zorb" or a 3x3 inch square of polyfilter in the power-filter chamber. Just one of these work-horse filters can take care of filtration in a freshwater tank of up to 40 gallons (depending on the biological load). With this particular system, I have observed that the use of two different types of filtration (biological under-gravel, and chemical) seem to work together synergistically, keeping water quality high over long periods, with few or no water changes required.
In nature, a huge variety of different biological and physical processes are involved in the cycling of energy and material. If it works in the real world it should work for us too.
Removal of sediment: At first glance, it might not be clear why I include this in a section on "filtration". The gradual accumulation of insoluble material is the natural consequence of biological processes. Organic sediment represents a stockpile of waste-products; the end point of the flow of energy through the system, and the natural consequence of the second law of thermodynamics. All ecosystems accumulate sediment, which is either laid down locally, or carried away by natural forces and deposited somewhere else. All enclosed bodies of water such as lakes and ocean basins gradually "silt up". Aquarium systems are no exception to this rule. Since I have defined filtration as "the input of energy to, or the exchange of materials with, an otherwise closed biological habitat in order to overcome the consequences of metabolism and the second law of thermodynamics" it seems locical to discuss it here.
Sediment is made up of inert organic material (detritus), and some inorganic precipitates that contain very little available energy. Sediment may also contain ligand-bound or otherwise trapped toxic materials such as heavy metals. In order to counter the gradual inexorable accumulation of sediment you will have to occasionally vacuum out some of the sediment from the bottom of each tank. Use the "vacuum tool", (a clear 2" diameter pipe attached to the flexible siphon tube) for this job. You don't need to suck out all the sediment, or try to "clean" all the gravel, since the sediment itself poses no threat to your specimens as long as it is laying inert at the bottom of the tank. In fact, a little accumulated sediment is desirable since it provides a home for many different invertebrates and protists. Your only objective is to prevent the accumulation of inches of fine sediment over time. You can draw out a little sediment from a different part of the tank every time you perform a water change, or scoop it out from wherever it seems to accumulate most quickly. Try not to stir up vast clouds of possibly toxic material, or suck up any valuable plants or curious animals.
You may also see some accumulation of sediment on rocks and plant surfaces. This should be vacuumed away if possible, or you can use a turkey baster to gently sweep exposed surfaces clean as though you were sweeping leaves with a leaf blower.
You can dispose of gravel free sediment straight down the sink if it is fine enough, or dump it into one of the decomposer communities ("Leaf litter" for fresh water sediment, "shore line" for marine).
Because our displays are permanent and set up as natural ecosystems, the gradual deposition of sediment is an inevitable reality. Given enough time, you will certainly have to remove a little sediment from of all of them.
Removal of sediment from our microcosms is analogous to the use of mechanical filtration in that the objective is to remove inert particles. The advantage of waiting until these particles sink is that this prevents loss of beneficial plankton. The Smithsonian microcosms have tried to include settling areas meant to automatically concentrate sediment near an outlet valve so that it can be easily disposed of. I observed first hand that these are not very effective because it is surprizingly hard to predict exactly where sediment is most likely to be deposited. It may eventually be possible to design some sort of effective sediment trap for use with our systems, but for now, physically removing observable accumulations of sediment seems to be our only option.
Water changes: At one time, before the development of modern filtration techniques to convert ammonia to nitrate, the only way to keep aquaria hospitable was through massive, frequent water changes. These no longer need to be performed quite so frequently but they are still an inevitable part of aquarium maintenance. All aquaria gradually accumulate some solutes that cannot be removed. Every time you add water to an aquarium to replace evaporation, you also inevitably introduce some impurities. These can begin to concentrate over time as you add many volumes of water to the system to replace evaporation. Other solutes that cannot be removed may come from dissolving minerals and accumulating biological wastes.
In addition, marine tanks are faced with the problem of a slow drift of the relative proportions of different ions present in the water. Different ions evaporate away or precipitate out of salt water at different rates, therefore, the salt water in a small closed system begins to resemble sea water less and less over time. Most aquarium texts recommend a weekly 5% water change for all tanks. I have found it more convenient (but still effective) to change 30-50 % of the water in our marine tanks every 6-9 months, 15-30 % of the water in the fresh water tanks once every 6 months -1 year, and 80% of the (small amount of) water in the leaf litter tanks every month.
Because marine invertebrates are very sensitive to toxic metals like copper, you should mix new sea water using only chemically filtered or distilled water, never raw tap water. Similarly, fresh water tanks should ideally be replenished using distilled or filtered water, or at the very least, tap water that has been agitated with an air pump and diffuser for >24 hours to "gas off " the chlorine. Do not use the commercial chlorine removing additives. These work by combining with chlorine to form chloramine which is slightly more easily removed from water. However, because chlorine is also easily removed by modern commercial absorbents, chlorine removers are now somewhat obsolete and they just become one more impurity in the water that needs to be removed.
Removing water from tanks as part of a water change is a convenient time to vacuum out excess sediment using the vacuum tool.
Water changes should also be performed immediately in case of known contamination or catastrophic deterioration of water quality. Signs of such a disaster include (but are not limited to): foul smell, possibly accompanied by milky or cloudy water, known spillage or accidental introduction of toxic chemicals, accidental use of salt water in a fresh water tank, excessive yellowing, large unexplained shifts in pH, ammonia levels or salinity, formation of excessive foam on the water surface, bizarre or obviously stressed behavior of the inhabitants and unexplained mortality. In the event that such a catastrophe does occur, act quickly to find and remove the source of the pollution. You may need to perform a large water change and / or introduce an additional source of chemical filtration to remove the contaminant (keep some spare, unused chemical absorbent and a spare power-filter around in case of such emergencies).
Periodically, you should use one of the commercially available water test kits to test for the presence of nitrate, or take a water sample to Byerly's in Grandview and have them test the water for you. If the water test indicates a high level of nitrates this may be evidence of generally poor water quality, and you may want to consider improvements to the filtration system as well as a water change. You should also occasionally test the pH of the various tanks using a pH meter or a test kit. Saltwater tanks should be between pH 8 and 8.4, freshwater tanks should be close to pH 7. If the pH is not correct you should find the cause of the problem rather than simply adding buffers, acids or bases, which will not have any effect lasting more than a few hours.
Resist the temptation to perform water changes in the event of mild blooms of green algae or anything other than very severe blooms associated with really bad smell of decay. Dangerous blooms are typically caused only by bacteria (milky-white water) unicellular cyanobacteria (blue / green water) or dinoflagellates (dark reddish or brown cloudy water). Most blooms are a simply a sign that you need to add more plants, light or filtration to help remove excess nutrients. Changing the water will probably introduce nutrients that will perpetuate the bloom. Another solution is to add more grazers or filter feeders to turn your bloom into a diversity - generating resource. Be patient, most blooms end naturally when the microbes exhaust some limiting raw material.
Absolutely, positively do not treat tanks with chemicals designed to kill any of the inhabitants. NEVER treat a microbial bloom by adding "cures" purchased from a pet store. This includes algaecides, pesticides, herbicides and copper (used to kill marine parasites). Be careful when adding trace elements or commercial plant food to marine systems, since some of them contain copper, which is toxic to marine invertebrates. Even antibiotics recommended by the pet store to treat sick specimens must be used with extreme caution as they can destroy the bacteria in the biological filters. If you absolutely have to treat a sick specimen, try to extract it from the tank and treat it separately, or feed it medicated food so that it gets the medication directly . It's generally a bad idea to start throwing chemicals into the tank because once they are in it 's hard (or impossible) to get them out.
If plant growth slows or stops after a water change (or at any other time) it may mean that your water is TOO clean. Water changes may need to be followed by addition of nutrients. Use commercial plant foods like "miracle grow" for fresh water systems, and commercial marine aquarium trace elements like Theil Co.'s "Vital Gold" for marine systems.The practice of adding plant food flies in the face of mainstream "fish tank" maintenance dogma which generally preaches the importance of NOT introducing nitrates or phosphates. A fish tank is not a real ecosystem and does not use nutrients anything like as quickly as a healthy microcosm. I therefore recommend you occasionally add nutrients to all your systems, especially if plant and macroalgae growth seem limited. It makes a big difference to productivity and diversity. Chemical testing reveals that supplemental nutrients vanish from the water and enter the food chain almost immediately.
UV sterilization: A UV sterilizer consists of a powerful short - wave lamp placed in such way as to irradiate a stream of water that flows past the lamp, killing anything in it. UV sterilization is expensive, and may actually be ineffective at its claimed purpose of removing pathogens from aquaria and degrading dissolved protein molecules. Even if it does what it says, UV sterilization probably has limited beneficial value to a natural ecosystem tank and may be harmful if it degrades too much natural bacterial flora. My advice - don't bother.
The only caveat to this suggestion is: keep an eye on the literature. I suppose it is conceivable that new research will reveal some sort of indispensible function that UV from the sun performs in nature, but I doubt it.
COMING SOON - The rest of the manual. It includes sections on lighting and other electrical systems, construction tips, specimen collection, and some case studies of our systems. WATCH THIS WEB SITE !
