Oscar

The Oscar (Astronotus ocellatus) is one of the most recognisable and popular cichlids in the aquarium hobby, widely distributed across the Amazon and Orinoco river basins of South America. It occurs in Colombia, Venezuela, Bolivia, Ecuador, Peru, Brazil, French Guiana, Paraguay, Uruguay, and Argentina, with feral populations also established in Singapore and the United States. In nature it inhabits the shallows of slow-moving or still waters in forested areas, favouring silt-laden white water habitats where it associates with submerged tree roots and marginal vegetation. The species is also known as the velvet cichlid, tiger oscar, or marble cichlid.

Oscars are large, intelligent cichlids reaching 25–35 cm (10–14 in) in standard length with a typical lifespan of 10–20 years in captivity. They are generalised omnivores that in the wild feed on smaller fish, insects, crustaceans, and zooplankton, and have even been observed using a 'playing dead' thanatosis strategy to hunt. A single adult requires an aquarium with a base footprint of at least 150 × 60 cm (approximately 540 L / 143 gal). They are notoriously messy eaters requiring efficient filtration and weekly water changes of 30–50%. Oscars are known for their interactive, personable behaviour and ability to recognise their owners.

In the aquarium, Oscars thrive on a varied diet featuring a quality cichlid pellet as staple, supplemented with live earthworms, prawns, river shrimp, and similar meaty foods. They should not be fed mammalian or avian meat such as beef heart. While not especially aggressive for a cichlid of their size, their predatory nature dictates they should not be combined with much smaller fish. Suitable tankmates include larger characins, anostomids, other large cichlids, and larger loricariid or doradid catfishes. Water temperature should be 20–28°C, pH 6.0–7.5, with hardness of 90–357 ppm. Numerous ornamental strains exist including tiger, red, albino, and long-finned varieties.