Oscar Fish – Profile, Care & Facts

The oscar fish is a member of the cichlid family and a popular aquatic pet. It is also called the Velvet cichlid or Walnut cichlid. Oscars are famous for their dog-like behaviors and intelligence. Once the oscars recognize you as their owner, they will be incredibly endearing.

Another important fact about oscar fish is that they grow relatively large. They will average between 12-16 inches, and you will need a large set up to keep them happy.

Oscars are also quite demanding on aquarium conditions, which is why they are more suited for experienced aquarists.

To provide the best aquatic environment for your oscar fish, you will need to learn some basics, including:

Oscar Fish Natural Habitat

Wild populations of the oscar fish inhabit South America’s Amazon Basin.

They have been recorded in Paraguay, Colombia, Ecuador, Uruguay, Brazil, Peru, Bolivia, and French Guiana. This fish is considered invasive species in Florida, China, and Australia.

Oscars can handle a surprising range of wild environments. Some populations have even been found in Alaskan waterways before winter.

This resilience has made them more of an ecological hazard in North America and China.

Oscars prefer slow-moving rivers and streams in their natural habitat. They like to hide amongst vegetation and submerged branches, and the substrate in these habitats is soft with debris and rock.

Although the sunlight is bright, the water is not clear, and the light is dimmed as it heads to the bottom of the water bodies.

Wild oscars have been known to reach 18 inches and over three pounds at maturity. They also grow quite fast at rates of an inch every month. The oscar fish are also territorial and aggressive, especially during breeding.

Oscar Fish Tank Requirements

Although oscar fish can live in a wide range of environments, there are few things to consider as a fish keeper. Below, I’ve highlighted  few things that you need to know before buying an oscar fish:

Tank Size

Juvenile oscars are only about 1 to 2 inches, and you may be misled to think that they will not grow enormous.

Under the right conditions, however, they can gain an inch every month and easily reach 10-12 inches.

The minimum aquarium size recommended for one oscar is 55 gallons. To ensure maximum comfort, allow for 75 gallons for one oscar and at least 100 gallons for two oscars.

Oscars will get stressed and eventually die if they are held in a small aquariums.


You can use gravel- or sand-based substrates in an oscar tank. Use only around an inch of the substrate to make cleaning easy.

You should also use a prefilter since the fish are notorious for digging up and spitting the substrate. It can be frustrating to keep replacing the filter if the fish keeps aiming the substrate at it.

Plants and Decorations

Keeping live plants with oscars is tricky because the fish love to destroy them. They especially love to uproot the plants as they dig through the substrate.

You can either use floating varieties like hornwort or hardy plants like the Java fern. Some aquarists choose to use artificial plants instead of betting on live ones.

Oscars appreciate the hiding spaces provided by artificial plants, rocks, and driftwood. The fish are also known to re-arrange their territories, and you want to avoid breakable ornaments.

Use durable objects like stone crevices and PVC tubes.

Oscar Fish Water Conditions

It is important to cycle your oscar tank for 6-8 weeks to ensure that it is safe for habitation. Before adding your fish, ensure that the temperature and PH are suitable.


The temperature of an oscar tank should range between 74-81 °F. Oscars are a tropical species, and they require warm waters at all times.

You will need a heater to maintain the required range, although oscars are notorious for damaging anything that you keep in the aquarium.

Glass heaters do not stand a chance, but you can use models made from metal or heavy-duty glass. Some heaters in the market are made from titanium and they have proven robust enough for oscars.

You will also find better luck with external thermometers to ensure that the temperatures are in the right range.


It is advisable to replicate the water conditions of the wild habitats of the oscars. The fish thrive in a PH of 6, and the PH of your tank should stay in the range of 6-8.

Although they can withstand a range of water hardness, aim to keep it between 12dH-15dH. Invest in a reliable testing kit and regularly test the water.


Oscars are quite sensitive to the presence of ammonia. It is crucial that the PH in an oscar tank never exceeds eight because ammonia will remain in a unionized form and become fatal to your pet.

Ammonia tests should be carried out regularly to safeguard the health of oscar fish.

You will also need effective filters to prevent the buildup of waste. Canister filters are ideal for large setups, although some of them can get expensive.

Oscars are very messy, and you need the most effective filtration system that you can get. Get a filter rated for a larger set up than yours as over-filtration is better than under-filtration.

Canister filters are recommended because they come with a spray bar that promotes oxygenation. If you have an exceptionally large aquarium, you may need to use a sump canister if there is no canister filter rated for your setup.

Oscar Fish Diet and Feeding Schedule

Wild oscars prey on worms, crustaceans, insects, and smaller fish, which they supplement with berries and plant matter. They will eat anything you offer, but you have to ensure they are getting the right kind of nutrition.

Provide them with cichlid-friendly pellet and flake foods and live foods like krill, bloodworm, and brine shrimp.

You can offer the occasional feeder fish like Rosy Red Minnow, although such fish will have a lot of fat and inadequate nutrients. Frozen peas are an excellent treat for oscars and it gives them plenty of energy.

You can feed your oscars two times a day. Baby oscars are especially greedy, and they will seem hungry at all times.

Feed the juveniles three times a day and scale back to two times once they attain five inches.

Oscar Fish Tank Mates

The oscar fish is infamous for being aggressive and territorial. You can keep an oscar-only tank to avoid any aggression since they can be kept together.

If you want a community tank, opt for large and passive species. Some tankmates to consider are:

Jack Dempsey Cichlid

The Jack Dempsey cichlid can reach a length of 10 inches. It has a striking appearance featuring a dark to gray coloration with countless green and blue iridescent spots.

Jack Dempseys, like oscars, like to establish territory, and you should observe the tank keenly.

Sailfin Plecos

If you want to keep plecos with oscars, the sailfin plecos make the ideal tank mates. They can grow up to 18 inches and will be too large for your oscar to eat.

The sailfin plecos is a largely inactive species and it spends most of its time dwelling at the bottom of the aquarium.

Plecos have an armored body however, and they are capable of injuring oscars if threatened.

Silver Dollars

Silver dollars can tame the aggressiveness of oscar fish. They act as dither fish by swimming out in the open and thereby indicating to the oscars that there are no predators around.

The body shape of the silver dollars also makes it seem larger than it is to discourage predation from the oscars.

Black Convict Cichlid

This cichlid has a gray body, black stripes, and greenish highlights on the fins. It grows to only 6 inches, but its speed will largely spare it from predation.

The black convict cichlid will quickly dart away as soon as it feels threatened.

Severum Cichlids

Severum cichlids are easygoing and docile. At eight inches, these cichlids are large enough to avoid predation from oscars.

Severum cichlids thrive in community tanks, especially amongst non-aggressive species like plecos.

Ornate Bichir

If you are keen on getting colorful species, consider the ornate bichir with its silver belly and light gold and black mottling and stripes.

They are a bottom-dwelling species, although they can be seen darting quickly to the surface and back down.

The ornate bichir averages at a size of 24 inches, and you will need quite a large setup to keep them with oscars.

Firemouth Cichlids

The firemouth cichlid is named for the bright red color developed by makes during the spawning season. They grow to about 6 inches and have a non-aggressive temperament.

Firemouth cichlids will opt to hide rather than fight oscars, so you need plenty of hiding spots.

Oscar Fish Breeding

Although oscars are easy to breed in captivity, they are hard to sex as both genders are nearly similar in appearance.

The only way to differentiate male from female oscars is by looking closely at their genitals.

The males have one sharp spike for fertilization while the females have an egg tube that retracts to their bodies.

Wild oscars breed in the rainy seasons, and some aquarists sprinkle water on top of their tank for 5-10 times several times a day.

You can also lower the temperature, and perform 20-30% water changes every few days.

Provide the mating pair with a breeding tank of at least 100 gallons. Decorate the tank with rocks since it is where they will lay the eggs.

The oscar eggs hatch after two to three days, and you will need to feed the juveniles several times a day to support growth.


The oscar fish is a bit rare in the aquarium trade since it is quite aggressive to catch in the wild. It can, however, be bred successfully in captivity, as long as the ideal conditions are adhered to.

You can keep the oscars with large and passive species while avoiding smaller fish that will be targeted as prey.

American Cichlids   Updated: May 11, 2022
avatar Hey, I'm Fabian, chief editor at Aquarium Nexus. I really enjoy the aquarium hobby and love sharing my experience with others. If you have any questions feel free to contact me or leave a comment below.

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