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Oscar Fish Essential Care Guide

Are you thinking about adding an Oscar fish to your aquarium?

These vibrant cichlids are known for their striking coloration, friendly yet sometimes aggressive personalities, and intelligence. But before you ‘take the plunge’ and bring one home, it’s important to know that caring for an Oscar fish requires dedication and attention to detail.

In this care guide, we’ll take a deep dive into everything you need to know about creating the perfect environment, feeding, and breeding, as well as common illnesses to watch out for.

Whether you’re an experienced fish keeper or a newcomer, this guide will provide you with all the information you need to give your Oscar fish the best life possible.

So, if you’re ready to start learning about the Oscar fish, then let’s get started.

Natural Habitat

Oscars, also known as astronotus ocellatus, are native to the slow-moving rivers and tributaries of South America, specifically in the Amazon Basin.

They’re typically found in areas with sandy or muddy bottoms and plenty of vegetation for them to hide and forage in.

In the wild, Oscar fish live in both freshwater and brackish environments where the water is slightly salty.

Appearance and Size

Oscars are a medium to large sized cichlid with adults reaching up to 12 inches (30 cm) in length.

There are reports of some Oscars reaching sizes as big as 18” (45 cm) however, most in captivity typically don’t grow larger than 12”.

They come in a variety of colors including red, orange, yellow and albino, and are known for their striking coloration and patterns. Oscars have a stocky body shape and a big mouth with strong jaws and teeth.

a lone oscar fish

Behaviour and Temperament

Oscars are known for their intelligent and curious nature. They’re relatively active fish and will often spend time exploring their tank and checking out their surroundings.

They’re also known to form strong bonds with their owners and can even learn to recognize them.

Despite their friendly nature, Oscars can be territorial, particularly when breeding, and may display aggressive behaviour towards tankmates.

Fish Tank Size and Water Parameters

Oscars require a minimum tank size of 55 gallons for a single fish and 75 gallons or larger for a pair. A bigger tank is always better as it allows more swimming space.

The water temperature should be between 72-82°F (22-28°C) and the pH should be 6.5-8.0.

They also prefer soft to moderate hard water. A sandy or fine gravel substrate and plenty of rocks, caves, and other hiding places should be provided to give the fish a sense of security.

Water changes should be performed every 3 to 4 weeks once you have established a good level of beneficial bacteria. For optimum health, all the specific water parameters for Oscars should be met. A test kit will help you attain the precisely needed environment.

To learn more on the nitrogen cycle for tanks especially when it comes to nitrites, ammonia, and nitrate levels, check out my article on the NITROGEN CYCLE for aquariums. 

Lastly, Oscars can be territorial so make sure to create an environment where all your fish can retreat and feel safe in.

I have another helpful article on using PVC in an aquarium which can be found here


Oscars are opportunistic omnivores and will eat a wide range of foods. They’re known to be voracious eaters and require a diet high in protein.

They’ll eat live and frozen foods such as brine shrimp, blood worms, and krill, crayfish, insects as well as pellets and flakes. They’ll also accept a small portion of vegetables such as spinach, lettuce, nuts, and some fruits.

You might be surprised to learn that Oscars require a diet rich in vitamin C. If their diet lacks the vitamin, they’ll end up getting sick. So, ensure you’re supplying foods with plenty of this nutrient.

Average Lifespan in Captivity and the Wild

The average lifespan of Oscars in captivity is around 10-15 years, with some living up to 20 years.

In the wild, their lifespan is generally shorter due to natural predators and environmental factors.

Recommended Tank Mates

Oscars are generally not recommended for a community tank. They’re territorial fish and can become aggressive towards other tankmates, particularly when breeding.

If you wish to keep them with other fish, it’s best to keep them with fish of similar size and temperament such as other large cichlids or catfish.

Suitable species can include (but not limited to) convict cichlids, severum cichlids, clown loaches, silver dollar fish, fire eels, red parrot fish, blue acaras, giant gourami, jack dempsey, green terror and bichirs.

As you can see, most of these fish are cichlids as well. I like the idea of having a bichir in the same tank as Oscars. I think that would make for an interesting and fun tank to watch.


Oscars are relatively easy to breed in captivity. They’re cave spawners and will lay their eggs (300 – 500) on a flat surface such as a rock or flowerpot or in a cave or other hiding place.

Once the eggs have been laid, the male will protect them and the female will guard the surrounding area. The eggs will hatch in about 3-5 days and the fry will be free swimming a week later.

If you have a pair of Oscars that you can breed, I’d recommend removing other species of fish from the tank. Give it a few weeks and observe daily for eggs appearing.

Once the fry is hatched, I’d suggest moving them to a smaller tank or placing them in a fry net in the same tank.

Once the fish are 6 to 8 weeks old, you can try placing some with their parents or just keep them in a separate tank until they’re a suitable size – which is big enough so an Oscar can’t easily devour them.

Common Diseases

Some of the most common problems include Ich, Fin Rot, and Dropsy. Ich is caused by a parasite and is characterised by white spots on the fish’s body.

Fin rot is typically caused by poor water conditions and results in the fins becoming frayed or discolored.

Dropsy is a bacterial infection that causes the fish to bloat and its scales to stick out. The fish bloats because of unnecessary water being accumulated in the abdomen.

It’s important to maintain good water quality and keep an eye out for any signs of illness in your Oscar.

As I always recommend, it’s good practice to have a sick tank setup and always running.

When you notice a fish acting differently such as lethargic or rubbing against things, it’s time to get it moved to the sick tank for treatment.

Sickness spreads fast in an aquarium. You can treat a tank with healthy fish. It’s just not worth the risk in my opinion to take the chance of all your fish catching a disease that could have easily been prevented.


The price of Oscar fish can vary, depending on the size and color of the fish.

On average, they can range from $10-15 for small fry to around $30-50 for adult size.

Albinos can be a bit more expensive because of their appearance. Red Oscars are usually the best price as they are much more common and available.

Pricing will be cheaper in regions closer to oceans and breeding farms. The further inland you go in North America, the higher the price to purchase this species.

Special Recommendations

There are only a couple of special recommendations I’d offer when it comes to the Oscar fish.

1 – Make sure the tank is large enough. Whether you have other fish with your Oscar or not, they need a large tank. If they don’t get the space they require, you’ll find them to be sickly and possibly aggressive. This can result in your fish having a shorter life span.

2 – As mentioned previously, Oscars require vitamin C in their diet. You can supply this via fruits or special fish food that has the vitamin added. Or, you can share some of your oranges.

Final Thoughts

In conclusion, Oscar fish make a great addition to any fish tank, particularly for experienced fish keepers.

They’re highly intelligent and active fish, known for their size, striking coloration and patterns.

Caring for Oscars requires a spacious tank with a suitable environment, plenty of hiding places and a high protein diet.

They can live for up to 20 years with proper care and attention. Consider this time frame when choosing to take one home as a pet.

They’re not typically recommended for community tanks due to their aggressive behavior, although it’s not impossible.

Finally, if you decide to take on the task of caring for an Oscar fish, be prepared for an interesting and rewarding experience.