Fish profile · Cichlidae

Oscar

Astronotus ocellatus

AquariumFreshwaterLeast Concern (IUCN)

A large South American cichlid frequently kept in aquariums. Wild fish have eye-like markings near the tail, while aquarium strains include red, tiger and albino forms; adults defend territories and can eat smaller fish.

Last reviewed 26 October 2026 · 5 sources

Photo of Oscar — (c) Matt Muir, some rights reserved (CC BY) · CC BY

Max length: 40 cm
IUCN: LC; Least Concern
Family: Cichlidae; order Perciformes

Category from the IUCN Red List, via GBIF (CC BY 4.0); it may lag the latest Red List assessment.

How big?

Linear scale · hand 18 cm

Up to 40 cm.

The hand is 18 cm long.

How to identify

Robust cichlid body with a large mouth.
Wild-type adults have ringed eye spots near the tail and dorsal fin; aquarium colours vary.
Juveniles show pale and orange wavy bands with spots on the head.

Habitat

Lowland rivers

Slow whitewater habitats, with shelter beneath submerged branches.

Diet: Fish, crustaceans, insects and some fruit or other plant material.
Native range: Amazon basin and other tropical South American drainages.

Aquarium care

Minimum tank: 265 L
Temperature: 22.2–25°C
pH: 6–8
Temperament: Semi-aggressive

More photos

Oscar, photo 2 — (c) Vincent A. Vos, some rights reserved (CC BY) · CC BY

Sources

Last reviewed 26 October 2026