Keeping and feeding
Day-to-day care.
Start with the biggest tank you can fit, ideally 300 litres or more for one adult, with a heavy lid. Use sand or smooth gravel and a few large, stable pieces of rock or wood with plenty of open space. Delicate plants will be dug up or eaten. Oscars like warm water around 24 to 27 °C. They are fine with neutral, moderately soft to medium-hard water, but they are messy. Good filtration matters more than exact numbers. A large canister filter or sump, cleaned regularly, is the norm. Change 30 to 50 percent of the water each week, vacuum the substrate and test for nitrate now and then.
For feeding, use a quality cichlid pellet or stick sized to the fish's mouth as the staple. Add frozen krill, mysis, prawn or earthworms a few times a week for variety. Feed growing juveniles once or twice daily and adults once a day or every other day. Remove leftovers promptly, and do not give in to begging.
Behaviour
How it lives.
Oscars are big, deliberate swimmers that use the middle and lower levels of the tank. They often rearrange the decor and gravel. They do not school and are usually kept singly or as a pair. Pairs can become very territorial when breeding. They are intelligent, recognise their owners and can be hand fed. Anything small enough to fit in their mouth will be eaten, so avoid small fish, shrimp and snails. Good tankmates in a big enough tank include other large, robust fish such as Severums, large Plecos, Silver Dollars, Geophagus and Jack Dempseys. With their size and heavy waste output they suit keepers with some experience more than true beginners.
Tank planning
Set it up well.
Keep the water at 24 to 27 °C and pH 6.5 to 7.5, with soft to moderately hard water (roughly 5 to 15 °GH). Oscars produce a lot of waste. Use strong filtration rated for well over the tank volume, such as a large canister or sump, with moderate flow. Change 30 to 50 percent of the water weekly. Keep ammonia and nitrite at zero and nitrate low, because poor water quality is linked to hole-in-the-head disease and fin rot. Acclimatise slowly by drip or float, and expect a new Oscar to sulk, hide or go pale for a day or two. Signs of good health are a strong appetite, clear eyes, intact fins and alert behaviour. Common mistakes are tanks that are too small, overfeeding, under-filtering and relying on feeder fish.
Practical details
Plan the space and routine.
- Origin
- The albino Oscar is a captive-bred colour form of Astronotus ocellatus. The wild species comes from the Amazon basin in South America, including Peru, Colombia, Brazil and nearby countries. There it lives in slow-moving rivers, lakes and seasonally flooded forest with soft, warm water. Captive-bred fish are generally hardier and adapt well to neutral tap water, as long as it is kept clean and warm.
- Max Size
- 30 cm
- Diet
- Carnivore. In the wild Oscars mostly eat insects, crustaceans, worms and small fish, with a little plant matter and fruit. In the aquarium, use a good-quality large cichlid pellet or stick as the staple and size it up as the fish grows. Add frozen foods such as krill, mysis, prawn and earthworms for variety. Feeder fish carry a risk of disease and are not needed. Feed juveniles small amounts once or twice a day and adults once a day or every second day, giving only what is eaten in a couple of minutes. Oscars beg constantly, so overfeeding is common and it fouls the water quickly.
- Tank Recommendation
- For a single adult, plan on at least 300 litres in a tank about 150 cm long and 50 to 60 cm deep from front to back. A pair needs 450 litres or more. Juveniles grow fast, so a small starter tank only buys you a few months. Use sand or smooth gravel, a few large rocks or pieces of driftwood, and plenty of open swimming space. Oscars dig up and uproot plants, so stick to hardy plants tied to wood, or artificial ones. Fit a heavy, secure lid because they can jump, and fix down the heater and equipment.
Tankmates and breeding
Look beyond the first day.
Choose tankmates that are too big to be eaten and tough enough to hold their own. In a large tank, good options include Severums, Silver Dollars, large Plecos, Geophagus, Jack Dempseys, Firemouths, Bichirs and Clown Loaches kept in a group. Avoid small fish such as tetras, guppies and rasboras, as well as shrimp and snails, which will be eaten. Also avoid very aggressive cichlids that can bully an Oscar, and slow, long-finned fish.
Males and females look almost identical, and they are hard to sex reliably from outside. The only sure sign is the shape of the breeding tube (papilla) at spawning time. The usual way to get a pair is to raise a group of juveniles and let them pair off naturally. Oscars are open-substrate spawners. A pair cleans a flat rock or the tank floor and lays hundreds to over a thousand eggs. Both parents guard the eggs and fry, often aggressively. The eggs hatch in a few days. Once free swimming, the fry can be fed baby brine shrimp, then crushed pellets. Breeding needs a very large tank and is mainly for dedicated keepers.
