How To Care For Oscar Cichlids (Astronotus ocellatus)

Oscar Cichlids

Last updated on July 21st, 2022 at 10:53 pm

Oscar Cichlids, also known as the Astronotus ocellatus, is one of the most popular aquarium fish in the world, with good reason—they’re beautiful, robust, and relatively easy to care for. They can grow up to 12 inches in length and are native to South America, including parts of Venezuela, Brazil, and Guyana.

Astronotus ocellatus, also known as the Oscar cichlid or calico bass, originates from the Amazon basin in South America and can be found in both the wild and in aquariums across the world today.

Caring for oscar cichlids can be difficult because they have special dietary needs and require plenty of tank space to swim around in. But if you keep these fish properly fed and in an aquarium with proper filtration, your Oscars will be able to swim around as much as they want.

They are freshwater fish belonging to the Cichlidae family, which includes hundreds of species of freshwater fish from Central and South America, Africa, and Asia. Their natural habitat is found in slow-moving rivers and lakes of these regions, with various species preferring slightly different environments.

As popular freshwater fish, they often get confused with their cousins from the genus Astronotus, since they are all known as Oscars in the aquarium hobby. Oscar cichlids have brown, green, or blue backs, but their most distinctive feature is the single black eyespot on each of their caudal fins, which gives this fish its name.

Below you’ll find everything you need to know about how to care for your Oscar Cichlids, including recommended tank size and setup.

Origin and descriptions

Oscar Cichlids

Oscar cichlids are natives of Central and South America. Astronotus ocellatus is a gregarious species found in rivers, lakes, and ponds in Venezuela, Brazil, Colombia, Guyana, Ecuador, and Peru.

They belong to a large family of cichlid fish known as the labrinth fish because they have a more complex labyrinth organ that allows them to draw oxygen from the air in addition to surface water. Astronotus ocellatus is also known as an Oscar or tiger Oscar cichlid, but these are all common names and not formal scientific designations.

Labyrinth refers to their ability to breathe using gills and through their mouth while ocellatus refers to the small black spot on each side of their tail fin. This species inhabits primarily Central America, but also can be found in parts of South America, Florida, Texas, and Mexico. Oscar fish will grow up to 12 inches long and will require a tank at least 55 gallons in size with plenty of hiding places. If you own Oscars you need to keep in mind that males are very territorial towards other male Oscars, especially if there is only one female per tank.

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Species profile

Oscar Cichlids

Oscar cichlids are native to South America and are known for their bright coloring and sleek shape. They can grow up to 12 inches in length. Oscar cichlids thrive in both fresh and saltwater aquariums. They’re compatible with many other fish species but will eat smaller fish so they need a home that can accommodate plenty of room and hiding places.

The Oscar is naturally skittish, so introducing it slowly into an unfamiliar environment may help it become accustomed to its new habitat. Use freeze-dried bloodworms or krill as treats when training your Oscar to perform tricks; most Oscars enjoy being fed live or frozen food but may take longer than some other breeds of fish to learn how to hunt effectively.

Natural Habitat and Scientific Information

Oscar cichlids are endemic to South America and Central America. These fish were first discovered in Uruguay by a man named Giuseppe Parini in 1872. They live in rivers and lakes with slow-moving currents that have sandy or mud bottoms. They inhabit waters with low nitrate levels, as well as soft water.

The pH levels must be between 6-8 while specific gravity levels should fall between 1.010 and 1.015 to maintain optimum health of these beautiful freshwater fish species. The temperature range where they thrive is 68-74 degrees Fahrenheit.

Oscar cichlids size

As juveniles, they are often sold at 1.3 inches (2.5-7.6 cm), as adults, they can grow up to 11-12 inches (28-30.5 cm)

Oscar cichlids tank size

The minimum recommended tank size is 55 gallons for a single fish and around 100 gallons for a pair.

Tank set up

You will need a 55-gallon or larger aquarium. Ideally, it should be long and narrow in shape, providing enough room for two fish on either side of the tank. This style of tank makes it easy to create several different zones with distinct habitats for your fish. However, if you have only one Oscar cichlid then a standard round tank can suffice as long as there is plenty of room for an elaborate setup.

The other option that has become popular recently is building a custom biocube for your Oscars. The nice thing about biocubes over conventional tanks is that they are made entirely out of acrylic, giving them great clarity compared to glass aquariums while keeping out impurities and harmful UV rays better than most acrylic tanks.

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Also, when set up correctly, they will mimic natural conditions much more closely which results in healthier fish. If I were starting out today, I would definitely get a biocube instead of a regular tank.

Oscar tank mates

The ideal companions for your Oscars are other large, non-aggressive fish. The general rule of thumb is that any tank mates should be at least twice as big as your cichlid. Don’t choose too many tank mates either; aim for a maximum of three fish per aquarium. The more fish in your aquarium, the more difficult it will be to maintain water quality.

Some good tank mates are large, peaceful South American cichlids such as pacu, swordtails, and convicts. You might also be able to keep medium-sized catfish such as plecos and giant danios with your Oscars, but only if you have a large aquarium—these fish can grow up to eight inches long. Bottom-dwelling varieties of tetras, barbs, and gouramis are also suitable; they get along well with cichlids because they inhabit different levels of the water column.

Breeding Oscar cichlids

Oscar Cichlids

Though they are called Oscars, A. ocellatus is not a species that breeds regularly in captivity. Although parents may guard their offspring, they rarely raise them past a few weeks of age. In fact, many aquarists find it easier to wait until eggs naturally hatch and raise fry separately than to encourage breeding at all. If you want to try your hand at raising A. ocellatus spawn, it’s important to have stable water chemistry with low alkalinity and high water hardness (15–35°dH).

More experienced breeders recommend keeping pairs together with another cichlid pair of similar size but different color or within one individual of a pair. Food should be primarily meaty fare such as beef heart, earthworms, and tubifex worms. Breeding adults are fed multiple times daily; young fish should be fed up to four times per day.

Filtering out uneaten food can also help reduce waste buildup and lower nitrate levels, which will make maintaining steady pH much easier if you choose to use peat filtration like Flourite Black Sand. Do not overfeed; heavy feedings will contribute to increased waste buildup and stress on your spawning pair.

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Similarly, avoid adding calcium supplements during breeding season because these cause rapid water chemistry changes when precipitated into tank water by fish excretions. Fry grow quickly and reach sexual maturity in about 6 months after hatching—although some experts say full growth takes about two years.

Are Oscar cichlids aggressive or peaceful?

Oscars are more aggressive than most other cichlid species and should not be housed with other species of cichlid fish, especially in smaller aquariums or bowls. They can be very territorial and dominant, fighting each other over territory on a regular basis if kept together.

They will also tend to view other types of fish as food if they can fit them into their mouths; remember that you aren’t buying a pet—you’re buying dinner! Even keeping two male Ocys together isn’t recommended unless you have an extremely large tank for them to live in.

Oscar cichlids care

Oscar Cichlids

Oscar cichlids require a fair amount of care and attention. They are one of many species of fish that can become aggressive towards other individuals in their group, so it is important to house them alone unless there is another fish that has been introduced into their tank first. Also, because Oscars are known to be extremely messy eaters, it is important to make sure there is enough filtration in their aquarium as well as adequate hiding places where they can retreat when they feel threatened.

Oscar cichlids diet

Oscars are omnivores but they feed mainly on meaty foods such as bloodworms, brine shrimp, daphnia, freeze-dried tubifex worms, and sinking pellets. They prefer to be fed multiple times a day, rather than just once daily. You should only feed your Oscar as much food as it can consume within three minutes or less; if you overfeed your fish, it could die. Offer new foods one at a time so you can identify any possible allergies or sensitivities.

Water parameters

Oscar Cichlids

Proper water parameters are crucial in cichlid keeping. The pH should range from 7.0 to 8.0, depending on which species of cichlid you keep and how sensitive they are to changes in pH levels. The water hardness should be high; ideally around 12dH but no lower than 8dH. All Oscars kept as pets should have hard water; their natural environment is found in soft and acidic waters where dissolved salts make it harder than normal.

Most importantly, however, is that a good quality filtration system must be used at all times. If your tap water does not contain enough minerals, then using a good quality reverse osmosis filter will ensure your cichlids get all of the minerals and trace elements that they need. You also want to use aquarium salt or freshwater aquarium salt mix; anything with up to 10% or higher concentration will suffice in order to help stabilize salinity levels and combat stress.

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Oscar cichlids lifespan

In captivity, they can live up to 20 years or more.

Parasites and diseases

Astronotus ocellatus cichlids are prone to fish diseases and infections as well as parasites like flukes, worms, and protozoa. The two most common issues are hole-in-the-head disease and ichthyophthirius, or white spot. Hole-in-the-head is a pretty common problem in tropical fish that causes small lesions on their head.

To prevent infection, make sure you’re using approved water treatments when necessary and that you quarantine new fish before adding them to your main tank.

White Spot Disease (Ichthyophthirius multifiliis) can be identified by white patches on your fish’s body, fins, gills, mouth, tail; it makes them more susceptible to fungal infections as well.


Although they’re not as cautious as some other fish species, Oscars are still wary of anything that might be viewed as a predator. The most effective and commonly used Oscars predators include: Piranhas, Arowanas, and Bluegills. New tank owners should especially be sure to keep an eye out for larger more aggressive fish such as these when introducing new cichlids into their aquariums.

Even herbivores can pose a threat; any plant-eating fish may try and compete with your Oscar if given enough time in its presence. Though cannibalism is not an issue specific to one single species, it’s particularly common in newly set up aquariums where food sources haven’t been established yet.

Do they make good pets?

The short answer is no, but that doesn’t mean you shouldn’t give them a try. Like most large, aggressive fish, oscars are not ideal pets. But if you’re looking for a predator with personality and a big appetite, they’re one of your best options.