Oscar care guide

Plan a tank with oscarsSee all tank mates

Oscar quick facts

• Known jumper: keep a tight-fitting lid.

Tank setup

One adult needs at least a 75-gallon (284 L) tank about 4 ft (120 cm) long, and bigger is better. A pair needs around 100 gallons (380 L) or more in a tank 5–6 ft (150–180 cm) long. Oscars dig and shove decor around, so use sand or smooth gravel, sturdy wood and big rocks resting on the tank floor. Fit a heater guard and a tight lid.

How many oscars in a tank?

The smallest common tank that suits oscars is a 75 gallon. Here is roughly how many fit in each size when they are the only fish, based on adult size and waste output. Leave room if you want tank mates.

Numbers are bioload limits only. Males fight, so keep one fish or one pair.

Water parameters

Keep it at 23–27°C (73–81°F), pH 6.0–7.5 and soft to moderately hard water. Oscars are messy eaters, so use filtration rated well above the tank size. Change 30–50% of the water every week to keep nitrate down.

Best tank mates for oscars

These popular species share oscars' water needs and temperament. See the full list of 11 good matches.

• Electric blue acara

  15 cm (5.9 in) · 23–27°C (73–81°F)

• Jack Dempsey

  20 cm (7.9 in) · 22–28°C (72–82°F)

• Siamese algae eater

  15 cm (5.9 in) · 22–26°C (72–79°F)

• Rainbow shark

  15 cm (5.9 in) · 22–26°C (72–79°F)

• Chinese algae eater

  25 cm (9.8 in) · 22–26°C (72–79°F)

• Senegal bichir

  30 cm (11.8 in) · 24–28°C (75–82°F)

• Kissing gourami

  20 cm (7.9 in) · 24–28°C (75–82°F)

• Ropefish

  35 cm (13.8 in) · 24–28°C (75–82°F)

Avoid keeping oscars with

• Betta fish: Oscar can eat bettas: they're small enough to fit in its mouth once it's grown.
• Bronze corydoras: Oscar can eat bronze corydoras: they're small enough to fit in its mouth once it's grown.
• Cherry shrimp: Oscar eats small shrimp like cherry shrimp.
• Common goldfish: They need different temperatures: Oscar 23–27°C (73–81°F), common goldfish 15–22°C (59–72°F).
• Dwarf gourami: Oscar can eat dwarf gouramis: they're small enough to fit in its mouth once it's grown.
• Guppy: Oscar can eat guppies: they're small enough to fit in its mouth once it's grown.

Feeding

An omnivore with a big appetite for meaty food. Use a quality large cichlid pellet as the staple and add earthworms, prawns, krill and insects like crickets, plus the odd pea or other vegetable. Skip feeder fish and mammal or bird meat. Oscars overeat readily, so keep portions small: two or three meals a day for juveniles, once or twice for adults.

Behavior

Less aggressive than their size suggests, but they eat any fish, shrimp or snail that fits in their mouth. They are territorial, and pairs can turn on tankmates when spawning. Good tankmates are robust fish of similar size, such as silver dollars, large plecos, severums and other medium-to-large South American cichlids. Many sulk for a while after water changes or decor moves.

Breeding

Oscars are hard to sex until they mature at around 1–1.5 years. The usual way to get a pair is to raise a group of juveniles and let two pair off, then rehome the rest. A pair cleans a flat rock and can lay up to a couple of thousand eggs. Both parents guard the eggs and fry fiercely.

Tips from experienced keepers

• Oscars are often sold at 2–3 inches (5–8 cm) but grow fast. Buy the big tank first.
• Don't feed feeder goldfish or minnows. They carry disease risks and are a poor staple diet.
• Use a heater guard or a heater inside the filter or sump. Oscars can smash glass heaters.
• Keep a tight, sturdy lid on the tank with no big gaps. A startled oscar can jump out.
• Hand-feeding is fun, but oscars beg even when full. Don't let the begging decide portion size.

Sources

We checked these references when writing this page. Values are for healthy long-term keeping, not survival limits. Last reviewed 2026-10-13. See our editorial policy.

• seriouslyfish.com
• fishbase.se
• aquariumcoop.com
• fishkeepingworld.com