Hatchet Fishes
The family of hatchet fishes, or Gasteropelecidae, is made up of a number of remarkable species with special characteristics which enable them to thrive just beneath the surface of the water. Their thin bodies and deep-bowed bellies give them a squeezed appearance, and their pectoral fins are large and wing-like. Anyone who has tried to raise hatchet fishes knows that they are among the most delicate of characins, requiring a great deal more care than the average tropical fish.
Hatchet fishes are found in many areas of tropical South America. Here they live both among plant banks and in open water, especially in places where tributaries meet larger rivers. At present only two of the species in this relatively small family can be kept for long periods in aquaria: Carnegiella Strigata and Gasteropelecus Sternicla. All other known species of hatchet fishes are extremely delicate, and it is difficult to keep them alive in the aquarium environment. Since few professional breeders raise hatchet fishes, they can sometime be considered a rarity.
In the past hatchet fishes were considered part of the family of true characins, or Characidae. However, more recent observations support the idea that the hatchet fishes make up a family independent of the true characins but similar to them. Hatchet fishes are specifically suited for life near the surface of the water. They have straight backs, mouths which slant downward, and dorsal fins set quite far back on their bodies.
Hatchet fishes are genuine "flying fishes." Their long, wing-like pectoral fins allow the fishes to make brief, buzzing flights over the surface of the water. During these flights their sharply arched bellies act like keels to provide stabilization. Strong pectoral muscles, which occupy a large part of the fishes volume, provide the necessary power for flight.
If you plan to keep hatchet fishes in your aquarium, be sure the tank is well covered. Otherwise these fishes are liable to spring up out of the tank, especially if they are frightened. In feeding, insects should be added the usual dry food as a replacement for the fishes' natural prey. With luck, hatchet fishes will spawn in aquaria, but successful beeding is rare. Nonetheless, a hatchet fish makes a fine addition to an aquarium of similar fishes, although this group does insist on leading its own existence relatively undisturbed by the other creatures in the tank.
Java Moss as a Living Backdrop
Vesicularia Dubyana, or Java Moss, is found in Indonesia, Malaysia, and the Philippines.This remarkably adaptable plant grows primarily along riverbanks but also in other dryer places. Java Moss is especially suited for underwater cultivation. Light and water conditions pose no problems for this a hardy plant. It gets its nourishment entirely from the water, and the tiny root hairs which grip the soil are for support only. Java Moss makes a beautiful backdrop for any aquarium. Start by entwining the moss strands around a plastic grid. Within a few months the moss will completely cover the grid, growing to a thickness of up to 2 inches. A living backdrop of this type is not only attractive but valuable as a natural filter. Java Moss in an aquarium helps to regulate the carbon dioxide and oxygen content of the water and reduces excess organic and inorganic matter in the tank. A Java Moss backdrop also provides excellent spawning and hiding places for the fishes.
The Fish That Has No Eyes
One of the most unusual denizens of the underwater world, the Blind Cave Fish (Anoptichythys Jordani) is found exclusively in subterranean pools and streams near San Luis Potosi in Mexico. As its name indicates, this fascinating characin is one of the few tropical fishes that cannot see. Years of living underground in caves and dark caverns have rendered the eyes of these fishes useless. Young Blind Cave fishes have small, very weak eyes which rapidly deteriorate and then disappear behind a layer of bone. The precise amount of eye degeneration varies from fish to fish, depending on the native waters, but all Blind Cave fish are sightless. This fish is uniformly pink in color and grows up to 3 1/4 inches in length.
Surprisingly enough, Blind Cave fishes have little trouble adjusting to life in an aquarium. These fishes are very peaceful and get along well with other fishes of their own size. A mysterious orientation system, apparently involving their lateral lines, keeps them from colliding with objects in the tank, and with their highly developed sense of smell they have little trouble finding food. These fishes swim around the tank rapidly, opening and closing their jaws in a constant rhythm as they search for food.
In nature, Blind Cave fishes live primarily on insect remains contained in the large quantities of bat feces which fall into the dark pools. In aquaria, Blind Cave fishes eat almost anything, although they prefer live food. Small, red rain worms make an excellant diet for these fishes.
Blind Cave fishes are very easy to care for. These fishes thrive in empty, unplanted aquaria, with dark sand or pepples on the tank floor. An 8 gallon tank should be large enough for about six average-size blind cave fishes. Since normal aquarium lighting is superfluous and can actually harm these fishes, it is best to put a weak light source at the side of the aquarium and let it shine through the tank. This creates a particularly dramatic effect and does not hurt the fishes.
Since aquatic plants cannot survive in the semi-darkness blind cave fish require, an effective filter or aerator is essential to maintain a safe oxygen level in the tank. Breeding these fishes is relatively easy, and the procedure is the same as for other characins. The spawning pair should be kept by themselves in a 10-15 gallon tank and should be removed immediately after the eggs have been laid. A double layer of marbles on the tank floor will prevent these fishes from eating their eggs. The young hatch after three or four days and are free-swimming within a week. Infusoria and tiny particles of dry food are the best diet for the rapidly growing young fry.
Living Lace
The Madagascar Lace-Leaf plant (Aponogeton Madagascariensis, formly A.Fenestralis) presents one of the strangest sights in the aquarium world. This is a plant that looks like the skeleton of a plant; the leaves, instead of being the normal solid mass of tissue, are rather a tightly interlocking network of tiny strands, a living sieve through which water flows freely. The aquarist with a green thumb and an eye for beauty cannot escape being captivated by this delicate water plant. It has enormous popularity, particularly among advanced aquarists.
As its name suggests, A. Madagascariensis is native to the island of Madagascar, where it grows in the shade alond river banks, both above and below the water. Like all Aponogeton species, it has tuberous roots. The leaves grow on long, thin stems and may reach lengths of as much as 8 inches, widths of up to 4 inches. Dark green to brownish in color, the unique lace-leaves consist of 5-8 parallel vertical veins, crossed by numerous smaller horizontal filaments. A dark central vein is prominent. Despite the delicate appearance of the leaves, they are actually quite tough.
Although the Madagascar Lace Leaf plant is not an easy species to cultivate, it will thrive in aquaria when its particular needs are met. These needs include indirect light; soft, slightly acid water (4 dH, pH 6.8-7.0); frequent partial water changes; and a temperature range between 64-68 degrees. Like other species in the genus Aponogeton, this plant has a resting period during which growth comes to a standstill. At this time it is best to cool the water to 55-59 degrees. One final consideration has to do with algae. This plant is very sensitive to it and great care must be taken to prevent algae growth on the plant.
Stones in the Aquarium
There are countless uses for stones and rocks in the aquarium. Take tank decoration, for instance. In addition to providing beauty and variety as individual ornaments in a tank, stones can also be used to hide filters, heaters, and other necessary but unsightly aquarium accessories. Another use is in tank landscaping, where rocks can provide firm support for terraces, ridges, and gently rolling hills of sand or gravel. And stones are not only of value to the hobbyist; they also offer numerous benefits to the creatures inside the tank. Almost all fish gain a feeling of security from the many caves and crevices that a good arrangement of rocks creates, and large, flat stones make excellant spawning surfaces for many egg-layers.
Like everything else in the aquarium, stones should be carefully selected to meet the requirements of the fish in the tank. Many of the more rapidly swimming species, such as barbs and danios, are found primarily in swiftly flowing streams in nature. Small, round stones are best for these fish, as they break up the dullness of a smooth tank floor without cutting into the fishes' swimming room. For smaller, more timid species, flat rocks piled one on top of the other can provide many nooks and crannies these fish need to feel comfortable in an aquarium.
A good suppy of large stones is absolutely essential in a tank containing big cichlids. These fish use rocks as protective hiding places, as spawning surfaces, and as landmarks to set off their different territories. One note of caution is called for: with large cichlids the hobbyist should be careful to place the rocks directly on the tank floor - it is amazing how quickly these fish can upset a whole pile of stones by digging away at the sand beneath the bottom rock.
Of course, it is possible to over do a good thing, and too many stones can hide all the fish. But when combined with plants and pieces of wood, stones add a rough, natural element to any tank. Stones that are highly attractive or unusual may also create some problems by drawing attention away from the fish. For this reason it is advisable to use mostly dark rocks that provide a neutral background against which the fishes' colors stand out. As to the types of stones; the choice of granite, basalt, and slate are the best choices. Limestone and rocks containing metallic elements can gradually alter the water conditions in a tank and are thus unsuitable for aquarium use.
