Oscar
Astronotus ocellatus
The Oscar (Astronotus ocellatus) is an aggressive fish that's rewarding to keep. Give it a tank of at least 360 litres (95 US gallons), water held at 68-82°F, and a pH of 6.5-7.5.
Captive lifespan reflects typical experience in a home aquarium, not maximum recorded age; genetics, sourcing, and care vary.
Natural distribution
South America
- South America
Regional colours match the stocking calculator's origin map.
Oscar Tank Setup
Give them at least 360 litres (95 US gallons). Cichlids are territorial and produce plenty of waste, so strong filtration and some rocks or wood to break up sight lines both help. Aim for 68-82°F and a pH around 6.5-7.5. They grow to around 35 cm, so plan the tank size and filtration for a full-grown adult rather than the small juvenile you see in the shop.
What Do Oscars Eat?
They're not fussy eaters - feed a varied diet, rotating good-quality dry, frozen, and gel foods rather than the same thing every day, and match the food size to their mouths.
Oscar Tank Mates
Requires a large tank and good filtration. Predatory; may eat smaller fish. The Oscar is aggressive, which is the first thing to weigh up when you choose tank mates. It's predatory, so anything small enough to fit in its mouth will be treated as food rather than a companion. Before you buy, run your full stocking list through our stocking calculator. It weighs temperament, adult size, and water needs together, which a single species page can't do on its own.
Are Oscars Good for Beginners?
Not a sensible first purchase. Get the tank cycled, keep easier fish stable for a year, then revisit if you still want the extra work this species demands.
Oscar - frequently asked questions
What size tank do Oscars need?
Oscars need a tank of at least 360 litres (95 US gallons). A bigger tank is always easier to keep stable, and gives them more room to settle in and behave naturally.
What water parameters do Oscars need?
Keep them at 68-82°F with a pH of 6.5-7.5, steady rather than chased to an exact figure. In a cycled tank, ammonia and nitrite should both read 0 ppm, with nitrate kept low through regular water changes.
What do Oscars eat?
Oscars are omnivores and aren't fussy eaters. Feed a varied mix of good-quality dry, frozen, and gel foods, and match the food size to their mouths. Feed small amounts once or twice a day, and remove anything they don't eat.
Are Oscars good for beginners?
It depends on the setup. Match Oscars to how often you actually test water and perform maintenance.
Common mistakes with Oscars
- Underestimating tank size - the minimum footprint is 360 litres (95 US gallons); impulse buying into a smaller tank leads to stress and shortened lifespan.
Guides that pair with this fish
- Oscar keeping watch-outs - Reality checks before commitment.
- Oscars with other fish - Tank mate sizing patterns.
- The one inch per gallon myth - Why generic rules fail large cichlids.
Building a community? Run the full list through the stocking calculator before you add anything else.
Great tank mates
Chosen from temperament, overlapping temperature/pH bands, plausible minimum tank footprints, and size versus yours in App-aquatic data. Hobby nuance always wins - verify stocking and temperament before purchasing.
Fish to avoid mixing with Oscars
These well-known species are commonly sold alongside this fish but are not recommended tank mates - verify before purchasing.
- Pea PufferPredator - Pea Puffer will eat or injure smaller tank mates
- Betta (Male)Predator - Betta (Male) will eat or injure smaller tank mates
- Serpae TetraFin nipper - will shred the fins of peaceful fish
