Stocking Fish Tips: Slowly add fish to your tank. Never go out and buy a bunch of tropical fish because your tank’s bio-load won’t be able to handle it. Slowly adding fish gives your tanks biological filtration a chance to catch up.
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Astronotus ocellatus is a species of fish from the cichlid family known under a variety of common names including oscar, tiger oscar, velvet cichlid or marble cichlid. In South America, where the species naturally resides, A. ocellatus 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 popular aquarium fish.
A. ocellatus have been reported to grow into a length of 45 cm (approximately 18 in) and a mass of 1.6 kg (3.5 lb). The wild caught forms of the species are typically darkly coloured 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 (Serrasalmus spp.) which co-occur with A. ocellatus in its natural environment. The species is also able to rapidly alter its colouration, a trait which facilitates ritualised territorial and combat behaviours amongst conspecifics. Juvenile A. ocellatus have a different colouration to adults and are striped with white and orange wavy bands and have spotted heads.
A. ocellatus is 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, USA 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).
Although the species is widely regarded as sexually monomorphic, it has also been suggested that males grow more quickly, and in some naturally occurring strains, males are noted to possess dark blotches on the base of the dorsal fin. The species reaches sexual maturity at approximately 1 year of age and continues to reproduce for 9-10 years. Frequency and timing of spawning may be related to the occurrence of rain. A. ocellatus are biparental substrate spawners though detailed information regarding their reproduction in the wild are scarce. It has been observed that the closely related Astronotus crassipinnis may, in times of danger, protect its fry in its mouth in a manner reminiscent of mouthbrooding geophagine cichlids. This behaviour, however, has not yet been observed in A. ocellatus. In captivity pairs are known to select and clean generally flattened horizontal or vertical surfaces on which to lay their 1000 to 3000 eggs. Like most cichlids, A. ocellatus practice brood care, although the duration of brood care in the wild remains unknown.