Oscar Fish Care and Species Profile

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One of the most popular freshwater tropical fish is the Oscar fish.

Even though they are known for being aggressive and territorial, they are also admired for their beautiful colors, behavior and intelligence.

They earned themselves the name “Water Dog” because they interact well with their owners once they have settled in. 

If you’re new to keeping this type of fish, it’s advisable to take some time to learn about their characteristics, specific needs and behavior.

In the following article, you’ll find all the essential information you need to know about Oscar fish and you’ll know if you are ready to keep them or not.

Oscar Fish Overview

Oscar fish are also called Velvet cichlids, Oscar cichlid, or Tiger Oscar and its scientific name is Astronotus ocellatus.

It is a freshwater fish belonging to the cichlids family.

Oscar fish originally came from parts of South America (Brazil, Paraguay, Argentina, Uruguay, Colombia, Venezuela, and Peru).

They can be found swimming through the freshwater Amazon and Orinoco rivers and have been introduced to different rivers worldwide, including waterways in Australia, Florida, and China. 


An average Oscar fish lives for about ten to thirteen years, however, some of these fish have been recorded to live up to fifteen years.

If they live in their natural habitat (the wild), they can even live up to twenty years. 

Their lifespan is one of the reasons many people like to get an Oscar fish so that they have enough time to bond with them and can take care of them for a long time.

How well you take care of them can influence how long they will live.

Baby Oscar Fish


Oscar fish are sold as small juvenile fish and at this stage, their size is usually about 1 to 2 inches.

Its initial size usually makes people assume it can not grow very big but this is not the case.

Within a year, they can grow to be 10 inches long and subsequently, a full-grown Oscar can reach up to 12 – 14 inches long. 

Their growth is monomorphic, so there are no apparent differences in the size or physical appearance between the male and female species.


The Oscar fish has black/ brown and orange patterns on their bodies; they were named Tiger Oscars and Marble cichlids.

However, not all of these fish have red or orange marbling.

Some come with green or olive bodies and the albino variations are usually white with red patterns.  

They have an oval shape with large heads, eyes and mouths. Their fan-shaped dorsal and anal fins run through their body length making them look prominent and chunky. 

At first, their colors are dull and the markings are pitch black, but as they grow, the colors become brighter and the patterns become more noticeable and beautiful.


It is common knowledge that Oscar fish are very aggressive and territorial and at the same time, being very clever.

This fish’s intelligence makes them recognize their owners and allows the owner to hand-feed them.

They show excitement by wagging their tail fin, which is why they are called Water dogs. 

However, their aggressive nature makes it almost impossible to house them with other fragile and smaller fish species.

When the Oscar feels its territory is being invaded, it will try to attack the invaders by chasing them around the tank, biting them and sometimes even eating them. 

In its natural habitat, Oscars prefer to hide in the privacy of plants and caves, even though they are social animals. 

They are more active during the day than at night and prefer large open spaces as they are quick and active swimmers.

Male and Female Differences

Due to their monomorphic nature, it is usually hard to know the difference between male and female Oscar fish because there are no prominent physical and behavioral differences.

One of the ways to find out what the gender of an Oscar fish is, is to flip them upside down to see their urogenital openings.

The females opening has larger holes for laying eggs, but you might not be able to know until they are reproductively mature.

Until they are reproductively mature, the size of the urogenital opening for both males and females are the same.

They reach sexual maturity after a year. 

Another way to know the gender of an Oscar fish is to notice the growth rate.

If you have more than one Oscar fish, you will see that the male grows faster than the female. 

Blue Oscar Fish

Types of Oscar Fish

Below are different types and colors of oscar fish detailing how to recognize them by their physical appearance.

Tiger Oscar Fish

Tiger Oscar fish is the common oscar fish and they are one of the original types from which all other variants originate.

As their name implies, they have tiger colors, orange and black.

However, they do not have similar patterns to the tiger.

Oscar fish have a distinctive design being a solid color (black or brown), and another color, forming lines and blotches in random patterns.  

The other color starts from their mid-body as they do not have any color from their lips down to the beginning of their dorsal fin.

Red Oscar Fish

The red Oscar fish is almost totally red, and the red color makes it hard to notice any patterns on their body (if they have any).

They are also one of the original Oscar fish.

Their body has a velvety feel and the edges of their body are black.

Black Oscar Fish

Black Oscar fish are also similar to red Oscar fish, with the body being black instead of red and having orange spots instead of black.

The black oscar fish is not an original variant, it is a crossbreed variant with black bodies and orange patterns.

Albino Oscar Fish

Despite albinism being a defect, Albino Oscar fish are lovely fish that capture attention.

They have a white body with red or orange dot-like patterns.

Many people love to have them because of their unique looks.

They are also an original variant.

Albino Oscar Fish

White Oscar Fish

You can easily confuse a white Oscar fish with an albino Oscar fish because of the similarity in their colors.

However, the white Oscar fish has a pigmentation of dull shades of pink that blends in with the white color making it more distinct.

It is a crossbreed variant.

Blue Oscar Fish

The blue Oscar fish has slightly different patterns from the common Oscar patterns.

It has different shades of blue that is present over it’s whole body.

This is a very striking fish that is a result of cross breeding.

Green Oscar Fish

As expected, their solid body color is green.

It’s patterns are circle-like with either black or yellow colors.

It’s fins are also dark green or yellow.

It is a crossbreed variant and is a rare find.

Green Oscar Fish new

Lemon Oscar Fish

The lemon Oscar has the same pattern as the red Oscar fish, but it is yellow with white underlay.

It is also a rare crossbreed but with a slight behavioral difference.

These fish are less territorial and have a more unlimited diet.

Veil Tail Oscar Fish

Veil tail Oscar fish are similar to the Tiger Oscar fish, but it has more prominent orange spots.

The main difference is their tail being longer than the tails of average Oscar fish. 

Florida Oscar Fish

This fish adapted to a new environment, thereby developing new features and characteristics.

It is mainly found in places like Miami lakes, Everglades, and the Tamiami trails in Florida.

Young Florida Oscar fish have spots on their heads, bodies and fins with their heads being predominantly black.

Adult Florida Oscar fish have blue-green bodies and fins with large black blotches.

They always have a black spot on their caudal fin that is surrounded by a red circle.

Oscar Fish Care

If you get an Oscar fish, it is important to know how to care for it.

This section will discuss the best setup and maintenance required for them.

Tank Size

Even though the initial size of this fish is about an inch or two, they grow to be large in a short period of time.

Their tank size should be about 55 to 75 gallons for one Oscar fish and add about 25 to 50 gallons of water for every Oscar fish you wish to add.

That means about 60 gallons of water for an Oscar fish, not less than 90 gallons for two, and so on. 

Due to its territorial behavior, Oscar fish prefer ample space as they get stressed out if they do not have enough room to move.

If you put more than one of them in a tight area, they will be more aggressive and suffer ill health due to stress.

In addition to the size of the tank, you should also consider its width.

A narrow tank will make it difficult for an Oscar fish to turn.

As your fish grows, ensure the tank is wide enough to avoid them bumping into the walls of the aquarium while turning.

Tank Habitat and Conditions

The tank should have a sand substrate like a river’s fine-grained sand with some rocks scattered throughout the tank.

They like a nice medium to strong water flow that mimics the flow of a river.

The water should be slightly warm with a temperature of about 74 to 81 degrees Fahrenheit as Oscar fish can not survive in a habitat colder than 55 degrees Fahrenheit.

It is important to keep the water parameters constant and ensure that the tank has a high quality filtration system.

These fish love to have caves available to hide in so make sure to add some of those.

You can also add plants to the tank.

Oscar fish do not typically eat plants but they can uproot them when they are digging through the substrate so they should be firmly rooted to avoid this happening.

Oscar Fish’s Diet

Oscar fish are omnivores, so there are various things you can feed them.

A balanced diet is required to promote healthy growth and care:

  • Algae Wafers
  • Brine Shrimp
  • Green Vegetables like frozen peas
  • High Quality flake or pellets
  • Small fish
  • Larvae
  • Frozen Food like Daphnia
  • Insects
  • Bloodworm
  • Krill

Do not feed your fish live feeder goldfish or minnows.

If you want to feed them live foods then rather raise a tank of guppies and use them for live food.

This way you can make sure that the live feeder fish are free of disease.

You can feed them once or twice a day as much as they will eat in a few minutes.

Never overfeed as this leads to pollution of the tank water.

Oscar Fish Diseases

Common Diseases

If not cared for properly then Oscar fish can contract several different diseases just like any other fish.

Hole in the head

Hole in the head is one of the most common diseases affecting them. It is caused by the parasite Hexamita.

Some of its symptoms include lesions in the head and body, lethargy, white sores around the eyes, and loss of appetite.

You can prevent the disease by constantly maintaining good water conditions and supplying a varied and complete diet.

This disease is easy to treat as long as it is caught early.

Fin Rot

It is a bacterial infection, and it is caused by poor water quality, low oxygen levels, and overcrowding.

It causes stress in the oscar fish, resulting in lethargy, blackened fins and loss of appetite.

Treatment usually requires antibiotics.

It is advisable to perform a 30% water change before adding any medication.

Adding aquarium salt can also be helpful.


Ich is a protozoan parasite disease.

It usually occurs when you introduce live food and new organisms into an aquarium.

Some symptoms of Ich are white spots on fins and gills, reddening of fins and fish rubbing their bodies against rough surfaces.

You can treat it by adding aquarium salt to the water regularly and increasing the water temperature.

There are some over-the-counter medication that you can use.

Suitable Tank Mates

Being aggressive and territorial, it is best for Oscar fish to be kept as a single species in your tank.

They prefer to be kept in groups or as a pair.

If you have a large enough tank then there are a few other fish that are able to live with Oscar fish but keep an eye on things and be ready to step in if needed.

These include large fish such as:

  • Arowanas
  • Jack Dempseys
  • Firemouth Cichlids
  • Large Plecos
  • Silver Dollars
  • Severum cichlids
  • Bichirs
  • Green Terrors
  • Blue Acara
  • Demon Earth Eaters
  • Banded Leporinus


It is possible to breed Oscar fish but it will not be easy as they are very picky when it comes to choosing a mate.

If you are lucky enough to have a breeding pair then to initiate breeding you will need to mimic their natural breeding conditions.

The first step is to lower the water temperature by a few degrees.

Then start doing some partial water changes every 2-3 days.

Start feeding the fish a varied diet of frozen and live foods to condition them.

If this works you should be able to observe your oscar fish displaying odd behavior like shaking their fins and opening their gills more than usual.

Oscar fish lay their eggs on rocks so make sure there are enough in the tank for them to choose from.

They can lay up to 300 eggs at a time.

Once the eggs have been laid then the parent fish will hover over them keeping them safe from other fish and allowing water flow over the eggs.

The eggs should hatch in two to three days after which it is recommended to remove both parent fish to stop them from eating the babies.

Place the fry in a small tank filtered by a sponge filter.

Feed them four times a day with specialized fry food.

As they grow bigger and bigger then you will need to keep moving them to bigger tanks.


An Oscar fish is the perfect choice for large tanks.

They are interesting and fun and will interact with you.

They are not the easiest fish to keep but provided that you offer them a varied diet, a well filtered tank and choose their tank mates wisely you will be rewarded with years of of fun and enjoyment.

Photo of author


Irma Bense is the founder of BetterFishkeeping.com. She has over 42 years of experience in keeping fish.She has kept both freshwater and saltwater fish through the years.She has extensive knowledge in breeding numerous species of fish from Show Guppies, Cory Catfish, German Blue Rams to Apistogrammas.You can learn more about Irma on the 'About' page.

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