Tropical Fish, any fish whose natural environment is the Tropics, for example, the waters of and around Africa, South and Central America, India, or Southeast Asia. In these areas, tropical fish have always had economic and ecological significance. Recently, their worldwide importance has been recognized because they are a plentiful source of protein-rich food, a means of control of mosquito-borne diseases, and a potential tool in medical research.

Beyond this, freshwater tropical fish have an intrinsic interest. Colorful, often exotically patterned, and generally small in size, they are collected and raised by hobbyists throughout the world. The keeping of exotic fish for pure pleasure has been practiced since ancient times; today it ranks as one of the most popular hobbies. Tropical fish are now often bred specially for the hobby market, chiefly in Florida.

Fish are kept in various kinds of aquariums. These range from simple tanks to elaborate systems that simulate a natural habitat with equipment for heating, filtering, and aerating the water, and with provision of appropriate aquatic plants and living organisms. Tropical fish can be fed on dried fish foods available in pet shops, or on brine shrimp, various worms, or Daphnia, a species of small crustacean. The fish should be fed daily only an amount that will be consumed within a few minutes. Overfeeding is the major cause of death among aquarium-raised tropical fish, and unhealthy conditions are caused when uneaten food decays at the bottom of the tank.

Like other fish, tropical species are divided into live bearers (whose young are born alive) and egg layers (whose offspring hatch from eggs fertilized in the water). Live bearers are easier to breed, but care must be taken to keep the young separate from the adults, which are cannibalistic. Egg-laying fish require specific long-term environmental conditions for survival. Popular among the live bearers are the guppy, swordtail, black mollie, and platyfish. Egg layers include, besides the ever-popular goldfish and angelfish, the fighting fish ,(see Betta) the zebra fish, so called because of the black-and-white striped pattern across its body, and the neon tetra, distinguished by its iridescent band of blue and green.

The hobby of keeping marine species native to tropical seacoasts and reefs is a relatively recent development. For these species aquariums filled with natural or artificial seawater must be provided. Such tanks should also be equipped with means of controlling the balance of acids and alkalines in the water. Breeding these fish in captivity is extremely difficult.