Oscar

Astronotus ocellatus

FreshwaterFish

Care at a glance

Temperature: 68–82°F (20–28°C)
pH: 6.0–7.5
Adult size: 13.8 in (35 cm)
Minimum tank: 95 gal (360 L)
Temperament: Aggressive
Social behavior: Solitary
Swim level: Middle
Difficulty: Medium
Breeding: Hard
Rarity: Rare
Origin: South America
Family: Cichlidae

Overview

The oscar is a large, intelligent cichlid that is usually kept singly or as a bonded pair, and it is best given a tank of its own or shared only with big, sturdy tankmates. It is predatory and territorial, will swallow any fish small enough to fit in its mouth, and can bully companions, so anything kept with it must be too large to eat and able to hold its own. It is a heavy eater and a messy fish, so it needs strong filtration and regular large water changes to keep the water clean. Feed a quality cichlid pellet as the staple, with occasional prawn, mussel and earthworm, and avoid a diet of feeder fish or plain mammal meat. Expect it to rearrange the tank, so use a sandy floor and secure decor. Plan for at least 360 liters for a single adult.

In the wild

The oscar is widespread across the Amazon and other river systems of tropical South America, living in slow, warm waters among submerged wood and roots. It is adaptable but does best in soft to neutral water, with a pH of 6.0 to 7.5 and a temperature of 20 to 28 C. Because it is such a large and messy fish, the priority is a big volume of clean, well-filtered water rather than a detailed scape. A sandy floor, a few large pieces of driftwood and rounded rocks give it cover and interest, while plants are usually uprooted and so are best left out or kept potted and sturdy.

Good to know

Astronotus ocellatus belongs to the cichlid family, Cichlidae, and commonly reaches around 35 cm, sometimes more, growing quickly when well fed. It is named for the ocellus, the eye-like orange-ringed spot at the base of the tail, which is thought to deflect attacks away from the real eyes. It is a substrate spawner that cleans a flat rock and guards its eggs and fry as a pair. Breeding is hard mostly because of the size of the fish and the difficulty of pairing them, since mismatched adults can fight fiercely rather than spawn.

Did you know

Oscars are known for their personality and are often called wet pets. They learn to recognize their keeper, can be taught to take food from the hand, and will follow movement at the front of the tank, which is unusual for a fish.