Tropical fish are any of a large number of small freshwater fishes native to tropical regions. Many tropical fishes are colorful and attractive, and keeping tropical fishes is among the most popular hobbies. Some people keep only one species of fish, while others prefer to keep various kinds of fishes. The choice depends on such factors as the size of the fish and their ability to get along with other fishes in the aquarium.
Generally, tropical fishes are divided into two groups: live-bearers and egg layers. The young of live-bearers are born live, while the young of egg layers hatch from eggs that have been laid and fertilized in the water. Among the most popular live-bearers are the guppy (Lebistes reticulatus), platys and swordtails (Xiphophorus), and mollies (Mollienisia). Popular egg layers include the neon tetra (Hyphessobrycon innesi), the cardinal tetra (Cheirodon axelrodi), angelfishes (Pterophyllum), and the Siamese fighting fish (Betta splendens).
A Definition of a Tropical Fish
There is no single group of fishes which may be called tropical exclusively, for practically all of them have relatives living in temperate waters. Moreover, many include species which, living side by side with other species of the same genera, still do not have that other necessary attribute, the ability to live in small tanks.
The single, unifying characteristic of "tropical" fishes is that they must be available in small sizes, and must be able to live in more or less stagnant water, as the water in a standing tank, of necessity, must be.
History of the Hobby
The art of keeping fishes as pets is very old, being practiced by the ancient Egyptians, the Romans, and the Chinese of antiquity. However, all these peoples kept fishes from their own local waters in climates normal to the fishes. The hobby of keeping exotic fishes goes back at least to the 17th century in England when foreign fishes (probaby paradise fish, but possibly goldfish, both from China) were mentioned by Samuel Pepys, who saw them in London. There have been many surges of popularity of these foreign fishes since then, but the hobby as we know it today started about 1880 in England.
The last great upswing in popularity started during the 1920's. Since that time, probably 1,000 potentially suitable species of fishes have been sent from all parts of the tropical world to the fanciers in North America, Europe, and Australia. Most of them, although desirable either in color, habit, shape, or all of these, were unable to adjust successfully to tank life. However, about 200 species have become established as domestic tank inhabitants, with about 50 species so well established that they are raised commercially in such great numbers that none are needed from their home environment.
Because of the activity of the fanciers, a number of kinds of fishes are constantly available for tanks which do not occur at all in the wild state. This includes such forms as the various color phases of the platyfish and swordtails, Mexican fishes which have been hybridized in domesticity, and the extremely handsome Siamese fighting fish. The ordinary domestic specimen of the latter fish is actually an aquarium derivative of a much plainer and small-finned fish from Thailand (Siam) and adjacent areas.
The bright colors and bizarre shapes of reef fishes from the tropical seas of the world have been, and remain, a constant challenge to the skill and ingenuity of the fish fancier. Contrary to fresh water, which improves its fish-keeping ability with age and use, seawater deteriorates in tanks, and only the hardiest of marine fishes can long survive in it. Since pure, clean seawater is not readily available to most fanciers, attempts to reconstitute natural seawater from its chemical components are constantly being made. These are reasonably successful for a relatively small number of littoral fishes. Such creatures are in great demand, with the demand being satisfied by a new kind of fisherman, the scuba (self-contained underwater breathing apparatus) diver, who can readily take a small colorful fish from the coral cavern to which it retreats under danger. This source of supply has introduced to northern fanciers exotic species of form, color, and pattern almost beyond credibility. However, the problems of keeping seawater fishes, unlike those of fresh water, are not readily solved, for there seems no simple solution.