Danios In The Aquarium
Danios (generaDanio and Brachydanio) are lively, easy to care for, and well suited for community tanks. These cyprinds are native to southern Asia and Indochina and are found primarily in ponds, lakes and calmer parts of streams and rivers, although the genus DANIO also occurs in clear, swift mountain streams. Their behavior resembles that of the smaller minnows. Danios are full of energy and should be kept with species as lively as themselves. These fish love to play just beneath the surface and they dart after food with lightening speed. Danios are at home anywhere in the tank-on the bottom, in the middle or near the surface of the water.
THE TANK: The smaller fishes of the genus Brachydanio can be kept in relatively small aquaria and the Zebra Danio (Brachydanio Rerio) is an excellant species for the beginning hobbyist with limited equipment. Fishes of the genus Danio are somewhat larger and require more space than Brachydanio species. Although they may be kept in smaller aquaria, danios like plenty of swimming room and if possible, it is best to keep them in large tanks, 40 inches or more in length.
The tank floor should consist of coarse sand with some large pebbles and round, smooth stones. A flat piece of petrified wood may be added to the tank bottom. These fishes do not dirty the water and normal filtering is usually sufficient to keep a danio tank clean. Danios prefer somewhat turbulent water which can be easily achieved with a water circulation pump.
THE PLANTS: Danios need plenty of room, so it is best to plant only the rear corners of the tank and sections of the back glass wall. Almost any plant may be used, even the most delicate. Elodea Densa, Hygrophila Polysperma, Vallisneria, and Ludwiga, as well as Amazon Sword plants and Java Moss are recommended. Large plants which take up a lot of space are not suitable for a danio tank and overplanting may be harmful.
CARE: On the whole, danios are very hardy fishes. They like clear water which is rich in oxygen. Replace 1/5 of the water in the tank with new tap water once a week. The Zebra Danio (Brachydanio Rerio) and the Pearl Danio (Brachydanio Albolineatus) should be kept in water between 64 degrees and 75 degrees; other danios require temperatures between 72 degrees and 79 degrees. Normal aquarium lighting is sufficient.
FEEDING: Regular feeding with flake foods keeps mature danios lively, healthy and promotes spawning. Live food may be fed as an occasional treat. The best diet for young danios are any of the prepared egg-layer foods that come in a paste form and baby brine shrimp (ARTEMIA). Danios are primarily surface feeders but also eat food as it sinks to the bottom of the tank.
BREEDING: Although water hardness and P.H. are relatively unimportant in regard to breeding, spawning behavior in danios is stimulated by sunlight. If possible, the female should be kept by herself in a small, planted tank for about a day. Then one or two males should be added in the evening. Spawning occurs in the early morning, if there is enough sunlight. The male leads the female into a thick clump of planted growth where they press tightly against each other. Eggs are large and numerous. To prevent the parents from eating their young, it is advisable to feed them white worms during spawning.
FISHES:The species of the genus Brachydanio are small fish about 1 1/2 to 2 1/4 inches in length. The Zebra Danio (B. RERIO), a magnificent dark blue fish with gold bands, is one of the most popular fishes in aquaria today. The Pearl Danio (B. Albolineatus) comes in two different varieties: one fish is greyish white in color; the other has a gold tinge. The Leopard Danio (B. Frankei) is silver-blue in color with grey spots. Although one of the most beautiful danio species, the Spotted Danio (B. Nigrofasciatus) is very difficult to breed.
The genus DANIO contains larger fishes and the Giant Danio (Danio Devario). This hardy, active fish comes from northwest India and is rarily kept by hobbyists.
Unusual Spawning Behavior Among Pearl Gouramis
One of the most popular of the gourami species, the Pearl or Leeri Gourami (Trichogaster Leeri) is also one of the most beautiful. This fish is a shimmering silver blue in color with a mosaic pattern of darkly outlined speckles covering most of its body. An irregular black line runs from the snout to the base of the tail, and males display a warm, orange-red shading on their bellies. These rather shy fish are native to Southeast Asia, where they attain lengths of up to 4 3/4 inches.
The spawning behavior of the pearl gourami is similar to that of other Trichogaster species. A large bubble nest is constructed and several "false matings" occur before the eggs are finally expelled in an extended fish "embrace." The male then carefully places the eggs in the nest, guarding them conscientiously. Spawning may last up to several hours and is fascinating to watch.
Although a great deal is known about the pearl gourami, there still remain a few unanswered questions, particularly in regard to spawning behavior. For example, in seaching for materials for the bubble nest, male pearl gouramis have often been observed to pick up mouthfuls of gravel from the tank floor and deposit them in the nest. The gravel, too heavy to be supported in the nest, slowly sinks back to the bottom. What is the reason for this apparently senseless activity? Until recently the most commonly held theory among aquarists was that, in the frenzy of spawning activity, the fish becomes confused and cannot tell the difference between aquarium gravel and lighter, more useful nest-building materials.
New research by the Finnish aquarist Kobylin clearly refutes this theory. Basing his conclusions on observations over the course of several years, Kobylin maintains that this unusual spawning behavior among male pearl gouramis has a definite purpose: the removal of defective or diseased eggs from the nest. Kobylin notes that the fine pieces of gravel spit into the nest by the male cling tightly to eggs which have been attacked by fungus, weighing them down and forcing them out of the nest. Normal eggs are apparently unaffected. In this way the pearl gourami checks the spread of fungus infection among the eggs by removing the diseased eggs while preserving the healthy ones.
This ingenious explanation has been confirmed by another European aquarist, Arend van den Nieuwenhuizen of the Netherlands. In an acticle in the german aquarium journal DATZ, van den Neiuwenhuizen writes about his own experiments with T. Leeri and notes that the amount of sand deposited in the nest is directly related to the number of diseased eggs. It appears that the male pearl gourami is not as slow-witted as hobbyists had once thought. Behavior that has been considered purposeless has now been shown to be an integral part of the vital process of brood protection.
Delightful and Unusual Rasboras
As a result of improved airline shipping, the number of tropicalfish species offered to the hobbyist has greatly increased. However, some fish which in the past were well known favorites have all but vanished from the scene, perhaps due to emphasis on new importations. Rasboras seem to be among these forgotten favorites, even though they are excellant aquarium fish. Of the somewhat more than 45 species in the genus Rasbora, approximately 25 have been imported. Only a half dozen of these imported have remained established in the hobby.
Rasboras are found in fresh water throughout southeast Asia. They occur primarily in Ceylon, Sumatra, Thailand, the Greater Sundra Island and the peninsula and archipelago of Malaysia. A few species are indigenous to East Africa, but these are rarily imported. For the most part, these fish live in large schools in the upper layers of both flowing and standing waters. There are two basic body shapes, one is slim and not deep-bodied, the other is short and deep-bodied.
Care of these fish in not difficult, and they will live a long life if the following conditions are provided:
(1) large tanks with ample swimming room,
(2) groups of 12 or more so they can swim in schools,
(3) subdued lighting, but enough to support the growth of large bladed or bushy plants which should be planted in thickets,
(4)temperatures of 75 - 79 degrees,
(5)soft, slightly acid water,
(6)peaceful tankmates,
and (7)adequate diet. Although many species of Rasboras will prosper on flake food, live foods should be fed to supplement their diet and provide variety. In the wild, Rasboras are usually predacious, eating large quantities of insect larvae and small crustacea.
The Harlequin Rasbora,R. Heteromorpha, is the best known species of the group. Fish frequently imported and sold as this fish are actually R. Hengeli, a closely related species. Close examination will show that the black triangle on R. Hengeli is much smaller than that of R. Heteromorpha, and the former fish is much slimmer and less deep-bodied than the latter. R. Vaterifloris is similar to R. Heteromorpha in that both are deep-bodied fish. By some strange circumstances, R. Vaterifloris has often been sold under the name - Ceylonese Fire Barb. This nickname indicates the geographic origin and coloration of the fish, but it is not a true "barb".
Breeding any species of the genus is a feat accomplished by only experienced hobbyists. The Drawf Rasbora, R. Maculata,is particularly difficult since the fry are extremely small. The deep-bodied Rasboras, such as the Harlequin, have proven more difficult to spawn than their slim-bodied relatives. Many of the species of these elongated Rasboras are very attractive. In order to find them, the aquarist should search the tanks of several dealers, looking for unidentified or misnamed fish. Success will bring a great deal of satisfaction since Rasboras offer a real challange to the aquarist.
Spawning the Dwarf Auatralian Rainbow Melanotaenia Maccullochi, the Dwarf Australian Rainbow, is one of the more popular tropical aquarium fish from Australia. It was first introduced to the United States in 1934 and has been a favorite ever since. The list of positive qualities this fish possesses is most impressive. It is peaceful, hardy, easily fed, spawns readily, does not its eggs, does not eat plants, and has brilliant markings. Deep red horizontal stripes are combined with silver sides, brown back, and yellowish green belly. The fins are pink, edged in yellow, and there is a double dorsal fin.
Sexing these fish is quite easy once they reached the breeding size of 2 inches. The male's dorsal fins are pointed while the females are rounded. Prior to spawning, a bright yellow or white stripe is evident in the male. It runs from the top of the mouth to the first ray of the dorsal fin on the dorsal surface of the fish. The females fill with eggs when ready to spawn. Water conditions for spawning are a pH of 7.2 - 7.6, water hardness of 200 ppm, and a temperature of 78 degrees. These are brackish water fish that need a good deal of marine salt in their water. Use about 1 teaspoon per gallon of water. A tank of at least 10 gallons is necessary, and a long 20 gallon would be best. These fish are primarily surface spawners, and their native habitat of swift-moving streams gives them plenty of running room. Add a good deal of hornwort or Myriophyllum to the tank. Strands should be anchored to the tank bottom and allowed to float upward. Distribute 3 or 4 air stones throughout the larger clumps of plants. This is done not because the fish are heavy consumers of oxygen, but because they prefer to spawn in the stream of air bubbles.
Conditioning M. Maccullochi is quite simple, and the standard dry food and frozen or live brine shrimp is sufficient. Place the fish in the breeding tank for a period of 7 days. Each day approximately 20 - 30 eggs will be produced. These hang like Christmas decorations on the plants, each one being suspended by a long filament. It takes 10 days for the first young to appear so the adults should be removed before this. Fry are very lively and remain near the surface swimming exclusively in vertical maneuvers. If the entire spawn is to be raised, infusoria should be fed. If only a few babies are desired, live baby brine shrimp are sufficient. By the end of a week the fry can survive very well on a diet of finely powdered dry food and brine shrimp nauplii. After two weeks, there will be some individuals who have outgrown their tank mates. These fish should be placed in other tanks since they tend to monopolize the food supply.
A total weekly spawn may consist of 200 eggs, so if all fry are raised, they should be moved from the spawning tank to larger quarters after a month. In doing this, be sure to keep the pH, hardness, and water temperature consistent, as the young are very susceptible to changes. Another important point to remember is this species' aversion to strong light. The breeding and raising tank should be covered with a thick layer of Duckweed. The eggs will quickly fungus if not protected, and the fry will hide and die of starvation if the light is too bright. In 4 to 6 months, if properly raised, these fish will attain a length of 2 inches and be ready to breed.
