Oscar: Tank Size, Tank Mates and How Many to Keep

Oscars are huge, clever fish that beg for food like a puppy. One oscar needs a very large tank and a very strong filter.

Adult size
11.8 in30 cm
Smallest tank
75 gallons284 liters
How many
One or more
Temperature
73–81 °F23–27 °C
pH
6–8
Temperament
Aggressive
Swims
In the middle
Heater needed
Yes

What size tank does an oscar need?

At least 75 gallons (284 liters). The smallest standard tank that works is the 75 gallon. A bigger tank is always easier to keep stable. We give the size for an adult fish, because the small fish in the shop will grow. Scientific name: Astronotus ocellatus.

How many oscars in each tank size?

This is how many each standard tank carries comfortably if oscars are the only fish in it. Share the tank with other species and the number goes down.

Keep one oscar per tank, whatever the size. Of the common sizes, these are big enough: 75 gallon, 125 gallon.

Check oscars against your own tank and other fish

Good to know

  • A very messy fish: plan on heavy filtration and big weekly water changes.
  • It eats fish small enough to swallow. Choose tankmates at least half its length.

Tank mates for oscars

These animals like the same water, are a safe size, and have a temper that fits. It is a match on paper: always watch new tankmates for the first week.

Poor matches

  • Betta: Oscar (about 12 in) can eat betta (about 2.6 in).
  • Guppy: Oscar is aggressive and will bully or kill peaceful fish such as guppy.
  • Fancy goldfish: Goldfish do best with other fancy goldfish.

Can oscars live with...

Questions and answers

What size tank does an oscar need?

At least 75 gallons (284 liters). The smallest standard tank that works is the 75 gallon. A bigger tank is always easier to keep stable.

How many oscars should be kept together?

One is fine. An oscar does not need company, though a large enough tank can hold more than one.

Can oscars live in a 10 gallon tank?

No. Oscar needs at least 75 gallons (284 liters), and grows to 12 in (30 cm), far too long for a 20 inch tank.

What temperature do oscars need?

73–81 °F (23–27 °C), with a pH of 6–8. In most homes that means a heater.

Can oscars live with a betta?

It is not a good match. Oscar (about 12 in) can eat betta (about 2.6 in).

More fish

Adult size, tank size and water ranges follow the mainstream care consensus (Seriously Fish species profiles and FishBase maximum lengths). Where sources differ we use the more cautious figure. Stocking numbers come from our stocking calculator.