Oscar

Astronotus ocellatus

Bold orange-black markings on a powerful fish; plan for adult space first.

A small shop juvenile grows into a large cichlid needing a broad aquarium footprint.

Adult length: Up to 35 cm (standard length, without the tail fin)
Water temperature: 20–28 °C
Lifespan: 10–13 years
pH: 6–7.5
Hardness: 5–20 dGH

Native range: South America: western Amazon and Orinoco basins.

Natural habitat: Favours quiet, shallow water, including muddy or sandy channels and ponds; also recorded from rivers and lakes.

Prey-sized fish can be eaten. Digging and rearranging décor; adults need far more room than the sales tank.

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Appearance and identification

This tiger-form oscar has a deep oval body, broad head, fleshy mouth and irregular orange-black markings. Red, albino and long-fin forms are the same species; colour is not a reliable way to sex it.

Social behaviour and territory

Plan around one adult first. Even paired fish can conflict; keep a separation and relocation option.

Compatibility limits

Adult size and predation matter first.

Space requirements

A 150 × 60 cm base for one adult; pairs or groups need more. Another reference is 75 US gallons for a single fish.

Aquarium environment

Digging and moving décor undermine delicate rooted layouts. Secure heavy objects and leave turning and maintenance room.

Diet and feeding

Use suitable complete cichlid pellets with controlled amounts of varied aquatic frozen foods; remove leftovers. Live feeder fish are not a long-term staple.

Sources