Astronotus ocellatus is a species of fish from the cichlid family known under a variety of common names including
Oscar Cichlid, Tiger Oscar, Velvet Cichlid or Marble Cichlid. In
South America, where the species occurs, Oscars are often found for sale as a food fish in the local markets, however, its slow growth limits its potential for aquaculture. The species is also a
very popular aquarium fish.
Oscars have been reported to grow to a length of 45
cm (18 in) and a mass of 1.6 kg (3.5 lb). The wild caught
forms of the species are typically darkly colored with
orange ringed-spots or ocelli on the caudal peduncle and
on the dorsal fin. It has been suggested that these
ocelli function to limit fin-nipping by piranha which
co-occur with oscars in its natural environment. Further
studies have suggested the ocelli may also be important
for intra-specific communication. The species is also
able to rapidly alter its coloration, a trait which
facilitates ritualized territorial and combat behaviors
amongst co specifics. Juvenile oscars have a different
coloration to adults and are striped with white and
orange wavy bands and have spotted heads.
Oscar Cichlids are native to Peru, Colombia, Brazil and French Guiana and occurs in the Amazon river basin, along the Amazonas, Içá, Negro, Solimões and Ucayali river systems, and also in the Approuague and Oyapock
drainages. In its natural environment the species typically occurs in slow
moving white-water habitats, and has been observed sheltering under submerged
branches. Feral populations also occur in China, northern Australia, and
Florida, as a by-product of the ornamental fish trade. The species is limited in
its distribution by its intolerance of cooler water temperatures, the lower
lethal limit for the species is 12.9 °C (55.2 °F).
A number of ornamental varieties of oscars have been developed for the aquarium industry. These include forms with greater intensity and quantities of red marbling across the body, albino, leucistic and xanthistic forms. A. ocellatus with marbled patches of red pigmentation are sold as red tiger oscars, while those strains with mainly red
coloration of the flanks are frequently sold under the trade name of red oscars. In recent years long-finned varieties have also been developed. The species is also occasionally artificially
colored by a process known as painting.
Oscar Cichlid's are popular as pets, and are regarded as intelligent by
aquarists. This is in part as they learn to associate their owners and food and
are purported to be able to distinguish their owner from strangers. Despite
their large size, and predatory nature oscars are relatively placid aquarium
residents best housed with other fishes too large to be considered food items.
Oscars are known to uproot plants, and move other objects in aquariums and are best maintained in volumes of 200-600
liters (52-158 gallon)s. Oscars are relatively tolerant of a range of typical
aquarium water chemistries, though its large size and messy feeding habitats
necessitates efficient filtration be installed on the aquarium. Oscars are
undemanding to feed in captivity and will accept a range of foods that include
pieces of fish and prepared cichlid foods.