Science Fair Project Encyclopedia
Siamese fighting fish
The Siamese fighting fish (Betta splendens) is one of the most popular species of freshwater aquarium fish. It is a member of the gourami family (family Osphronemidae) of order Perciformes, but was formerly classified among the Anabantidae. It is native to the Mekong basin in Southeast Asia.
The natural colouration of B. splendens is a dull green and brown, and the fins of wild specimens are relatively short; brilliantly-coloured and longer-finned varieties have, however, been developed by breeders (see In the aquarium, below.)
In the wild, the Siamese fighting fish inhabits standing or slow-moving water, including floodplains and rice paddys, at temperatures of 24–30°C (75–86°F). Carnivorous, it feeds on zooplankton and mosquito and other insect larvae.
The Siamese fighting fish is often called simply (if imprecisely) by its generic name, which is then treated as a common name ("betta").
Both instinctive and learned behaviours of B. splendens have been studied in considerable detail. Its characteristic aggressive responses are readily elicited by its own reflection in a mirror placed outside an aquarium. The capacity to turn aggressive behaviour on and off in this way, without putting the subject at the risk of physical damage inherent in staging an actual aggressive conflict, made the fish a popular subject of study by ethologists and comparative psychologists interested in studying aggression. There was a stream of research on the fish's aggressive behaviour from the 1970s, though this has reduced lately, partly because of new approaches to studying aggression arising out of sociobiology, and partly because it was realised that, even if no tissue damage was done, repeatedly eliciting aggressive responses in the fish might be a source of stress. Interesting results were obtained, however; for example was shown that the presentation of such an aggression-eliciting stimulus will act as an unconditional stimulus in classical conditioning, and as a reinforcer in operant conditioning. It is as if the fish finds the opportunity to attack another fish rewarding.
In the aquarium
Because of its beautiful colours and fin shapes, the Siamese fighting fish is popular with aquarists. In Asian countries they have long been used in a sport similar to cockfighting, where it was necessary to have aggressive short-finned fish. But today, by selective breeding, it is not uncommon to see males with an array of colors and tails. B. splendens specimens are bred for tail shapes ranging from the common veil-tail to the much-desired 180° "half-moon" tails, while still showing a stunning array of colors: marbled, Cambodian, butterfly, and chocolate are just a few examples.
To keep an individual B. splendens, a minimum tank size of 1 gallon is recommended, if it will be kept in a warm room. A larger tank of 5 gallons will allow use of a heater, to maintain a temperature of about 27°C (81°F). The floor of the tank should have, as a minimum, a thin (5 mm or 0.25 in) layer of gravel to increase the surface area for nitrifying bacteria to colonize. Decorations can provide hiding places, especially important when two males are housed in a divided tank, or when the betta is living in a community tank. Every decoration must be free of rough areas or sharp points which can damage the delicate fins of the betta—for this reason, silk rather than plastic plants are recommended. Live plants will improve the water quality.
In Canada and the United States, the Siamese fighting fish is sometimes sold in a vase with a plant, with the erroneous claim that the fish can feed on the roots of the plant. Betta species are carnivorous, though, and an appropriate food must be provided, such as dry "betta pellets" or live or frozen bloodworms or brine shrimp. When kept in a small container such as a vase, the fish need frequent water changes, and the container must be kept in a warm room. A larger tank with a heater will provide better living conditions. Wherever the fish is kept, water must be treated with an appropriate water conditioner before use.
Because of the aggressive nature of this species, tankmates must be chosen carefully, and two male B. splendens should not be housed in the same tank unless they are separated by a dividing wall. Females may or may not be able to coexist peacefully in the same tank depending on their temperaments. Before co-housing Siamese fighting fish with other species, their compatibility should be carefully researched, and the owner should have a back-up plan if the shared tank does not work.
- Betta Talk (breeder's site with care information)
- Bettatudes (discussion forum)
- BettaForums (discussion forum with additional information)
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