Oscar Fish: A Guide to Care, Breeding, Diet & Behavior

Oscar fish are one of the most popular aquarium breeds who are known for their intelligence but are also famous for being aggressive. This may come as a shock to new hobbyists as they watch them swim gracefully through the water.

For this reason it is important that you know as much information as possible if you plan on keeping Oscar fish. They are hard to resist due to their attractive colors and appearance with an amazing personality.

This guide will teach you everything you need about these temperamental creatures that should only be looked after by fish keepers with a little more experience.


The Oscar fish who’s scientific name is astronotus ocellatus and belong to the cichlid family is native to South American countries such as Brazil, Ecuador, Columbia, and Peru.

You can find them pretty much anywhere in the Amazon River Basin and surrounding areas due this location being one of the most bio diverse environments on the planet.

They typically live in places that act as hiding spots such as slow-moving white waters with low-flow where predators cannot easily get to them. The species has a great personality but require a bit of experience to handle them due to their aggressive nature.

Typical Behavior

Oscars can be very aggressive fish and are also very territorial which means they will attack any fish that enters their territory. Their aggression can also be further fueled during mating and feeding times.

Although you will see down towards the substrate as they search for food, a majority of the time they can be found in the mid-levels of the tank. It’s important to ensure everything in the tank is secured down because they will often uproot plants.

Although Oscar fish are aggressive in nature, they are also amazing fish who can be controlled with the correct setup and tank mates.

Gender Differences

You can visually see the small external gender difference between a male and a female Oscar by flipping them upside down to see their urogenital openings. A male will have holes that are similar size, but a female has an opening for their eggs which is larger.

Both male and female will have holes that are the same size if they are not reproductively mature.

Different Types Of Oscar Fish

Let’s take a look at the different types of Oscar fish.

Red Oscar Fish

Red Oscar Fish

Distinguished by their bi-colored bodies, the red Oscar fish are one of the most iconic variants and an original “parental” type of Oscar fish. They have a velvety texture and a mix of black and fiery red.

Tiger Oscar Fish

Tiger Oscar Fish

One of the most popular and well known types of Oscar fish due to their name and distinguished tiger-like patterns. They are also one of the original breeds of Oscars and many other breeds originate from this variant. They are also a parental type varient.

Albino Oscar Fish

Albino Oscar Fish

Albino Oscar fish are white in color featuring bright while scales and have a smooth texture. They aren’t completely white because you can see reddish or orange in the lower parts of their body. Along with the red and tiger Oscar fish, this is also a “parental” type.

Black Oscar Fish

Black Oscar Fish

Black Oscar fish is a crossbreed variant with black bodies with tiger-like patterns across their scales and light, pale bands running across.

White Oscar Fish

White Oscar Fish

These are also a crossbreed variant that shouldn’t be confused with the Albino Oscar. They have dull shades of pink pigmentation that blends in so well that it gives them the appearance of being white.

Lemon Oscar Fish

Lemon Oscar Fish

Another crossbreed variant who have a yellow gradient over a white body. Although they are slightly calmer and less territorial than other members of the Cichlidae family, they will still eat everything that they possibly can.

Green Oscar Fish

Green Oscar Fish

A rare crossbreed variant with very interesting and intricate patterns. Some green Oscar fish have shades of black and yellow on their bodies. You will also see yellow-colored-circle like shapes and some with dark green bands and yellow scales.

Blue Oscar Fish

Blue Oscar Fish

This crossbreed are identified by contrasting shades of blue on their bodies, and patterns that are not seen in other types of Oscar fish. You will see dark bleu lines as well as brighter shades of blue that really pop out.

Veil Tail Oscar Fish

Veil Tail Oscar Fish

They have a longer tail than other types of Oscar fish which often feature bright orange spots that run all the way up to their head.

Florida Oscar Fish

Regional variants of Oscar fish with their own distinct traits and characteristics have also developed over time. As the name suggests, this variant originates from Florida, USA. You will often find them in places such as Everglades, Miami Lakes, and Tamiami trail.

They have orange rings over dark-colored bodies who can alter their appearance, but look similar in appearance to Tiger Oscar Fish.

How To Setup Your Oscar Fish Tank

It’s important that you have a correct tank setup to ensure your Oscar fish have a long and happy life. This section will teach you everything you need to know in order for you to have the best setup possible.

What’s The Best Aquarium Size For Oscar Fish?

Having an aquarium that is too small can cause overcrowding which can lead to your fish becoming distressed and develop stress-related health conditions. Here’s a general guideline you can follow:

  • 1 Oscar fish: 75 gallons
  • 2 Oscar fish: 125 gallons
  • 3 Oscar fish: 150-200 gallons

The Best Type Of Substrate

Both gravel and sand work well as substrates for Oscar fish. It’s important to remember that Oscars enjoy digging, as well as taking in substrate and spitting it back out. This can be a bit of an issue because it can cause filters to break.

The solution to this is to invest in a pre-filter. The job of a pre-filter is to trap debris and particles before the water even reaches the main filter. This will protect your main filter and could potentially save you a ton of money in the long run.

You should also use substrate sparingly and avoid putting too much down. One of the reasons for this is because any uneaten food and even debris will over time sink into the substrates.

What Kind Of Filtration Do Oscars Need?

As Oscar fish are very messy and sensitive to any water changes, a high-quality filtration system is crucial to ensure they stay healthy. As a rule, your filtration system should be so strong that it is capable of turning the volume of the water over four times per hour.

For best results, it’s good to have both a canister filter, as well as a backup such as a hang on back (HOB).

Lighting For An Oscar Tank

When it comes to lighting, just a standard room with natural light will work great. There’s not a need for any kind of special lighting, but adding some extra lights in there will not cause them any harm.

If you do add your own lighting, just remember that most Oscars prefer moderate-low lighting. This means that your Oscars will become distressed if you leave the lights on for any longer than 12 hours.

After adding the lighting, keep an eye on your Oscars to see how they react to it. If you feel it is effecting them in anyway, either dim the bulb or remove it completely.

Plants And Decorations

Plants and decorations play an important role which makes Oscars feel safe as they have a number of options to hide amongst. As they can often be found moving small objects around their habitat, it’s best to avoid ceramic or other decorations that are breakable.

Also be aware of your choices of plants. Oscars have a tendency to destroy real plants and they will not last long in you aquarium.They are also very clumsy and can often be seen bumping into things. For this reason, it is best to avoid adding sharp decorations.

The best options to go with are sturdy decorations, stone, caves, PVC pipes and fake plants.

It’s also best to avoid adding limestone, coral, or any other calcium-carbonate based minerals as these can effect the pH of the water and Oscars are sensitive to these kind of changes.

Creating An Ideal Habitat For Oscar’s

What Water Temperature Do Oscars Require?

As Oscar’s are native to South America, they thrive in warm waters. Your aquarium should be around 77 degrees Fahrenheit (25 degrees Celsius). It should be kept stable and ideally remain between 74 and 81 degrees Fahrenheit (23.5 – 27 degrees Celsius) at all times.

Water Flow

It’s ideal to have a flow that has a water turnover of 4 times per hour which produces moderate-high flowing water just like their natural habitat.

PH, Acidity & Basicity/Alkalinity Levels Be For An Oscar Tank

As with the water flow, the key here is to replicate what it would be in the wild. The toxicity of the water can be effected if the pH is not right. This means your Oscars can get ammonia poisoning. Here are some key points:

  • Oscars prefer a pH of around 7.2.
  • pH should be stable at all times and stay between 6 and 8.
  • You can increase the pH if it is too low using salts and pH changing kits. It’s important to do this minimally and not make drastic changes.

Chlorine And Chloramines

Bacteria can be killed when chlorine is added to municipal water. It’s important to remember that it is a highly-toxic gas that is harmful to fish, amphibians, and mammals.

As mentioned in the previous section, ammonia is also toxic. So when chlorine and ammonia combine together, it forms a products known as chloramines. Serious harm can to your fish can be caused by this poisonous chemical cocktail.

What’s the solution?

When adding fresh water to your aquarium, it’s important to use a dechlorinator. It’s role is to remove chlorine and chloramines, as well as other trace metals such as lead and mercury.

As Oscar fish are sensitive to water changes, always remember to never directly add tap water to your aquarium without first dechlorinating it.

Before you go any further, use a chlorine test kit to measure the quality of the water to ensure that all of the dangerous compounds have been removed.

Ammonia, Nitrite, And Nitrate

Ammonia is produced as a waste product from most aquatic fish, including Oscar fish in a unionized form which is highly toxic. As Oscars are highly sensitive to ammonia levels, it’s important to understand these changes in order for your fish to stay healthy.

Ammonia will stay in it’s toxic, unionized form if the pH levels are too high. We mentioned previously that the ideal pH is between 6 and 8. If the levels go above an 8 then this can kill your Oscars. Ammonia toxicity can also increase by water temperature.

The solution to preventing ammonia toxicity in your aquarium is to use a ammonia test kit. The best thing is you can pick these up pretty cheap from places like Amazon.

As well as Ammonia, nitrite and it’s byproduct, nitrate is something else you need to keep an eye on. It is a product of ammonia, and although less toxic, a build up of it inside of your tank can still cause problems for your Oscars.

The reason being, algae blooms can develop as a result of large amounts of nitrite/nitrate. This algae can produce toxins which lead to disease and can be harmful for your fish.

The easy solution to this is to just change the water on a regular basis.

Suitable Tank Mates

Oscars are not the greatest at making friends due to them being aggressive and very territorial. In the wild, Oscars live in diverse area where they are used to being around a lot of fish.

The problem in an aquarium is there is much less space. Oscars can be very aggressive towards other tank mates during spawning times. They are even well known to bully and be aggressive towards one another in a tank that is too small for them.

One option for potential tank mates is fellow cichlids such as Convict Cichlids, Firemouth Cichlids, Jaguar Cichlids, and Severum Cichlids.

By far the best option that is going to cause the least hassle is to simply have an Oscar only tank.

Oscar Dietary Requirements And Feeding

What Can I Feed My Oscar?

It’s always best to replicate an Oscar’s natural diet as much as possible. Let’s take a look at some of the options.

  • Live Fishes: Although this shouldn’t be the only food you feed them.
  • Insects/Worms: Mealworms and crickets are a great option. It’s best to get these from a pet supply to ensure that they haven’t been exposed to chemicals.
  • Prepared Foods: Tablets, pellets, flakes, crisps, and wafers.
  • Fresh/Frozen Foods: Scallops, shrimps, squid, and clams.

How Often Should I Feed My Oscar?


These are small Oscars of around 1½ to 3 inches which should be fed at least twice daily. Although you may need to experiment with this as this is a rough estimate.


When they reach around 4 inches long, they are now subadults. At 4 to 6 inches long you should still be feeding them daily, but you can alter there schedule such as one day feed them twice, but then only feed them once the following day.


Oscars are considered adults when they reach 7 to 8 inches, and should be given a very wide assortment of foods.

You can feed them every-other day at this stage, but keep a close eye on them. If you see that they become a little chunky, experiment with the feeding schedule.

How Long Can Oscar Fish Go Without Eating?

Oscars can surprisingly go between 2 and 4 weeks without eating. Larger fish can generally go longer without food. The length of time also depends on on the strength of your fish.

This means that if you having been feeding them well and you have strong adult Oscars, they can go longer without eating.

Breeding Oscar Fish

As Oscars are very picky about who they choose to mate with, they are one of the hardest fish to breed. This is yet another reason why it is best to have Oscar only tanks, as they prefer certain conditions. Here are the best two options:

  1.  You look around and buy a pair who are already established when it comes to breeding.
  2.  Buy a group of juveniles so they build a better connection as they will grow together.

The only problem with the second method is that you will have to be patient, as the breeding process won’t happen until they have matured which takes 1-2 years.

How To Initiate The Breeding Process

Oscars prefer breeding during rainy seasons out in the wild, so for best results you can replicate these conditions in your aquarium. Here’s how to do this:

  • Every couple of days, conduct 20-30% water changes.
  • Lower the temperature by a few degrees.
  • A few times  a day for 5-10 minutes, use a watering can to sprinkle water which replicates the effect of rain. This can be a pain to do manually, but the solution insteas is to us filter spray bars.

Disease, Illness, And Treatments In Oscar Fish

Although it’s very rare that Oscar fish get sick, there are certain things you need to be aware of. One of the most common things is what’s known as ‘hole in the head’ disease.

If you notice holes and cavities starting to form across their head, you’ll know that your Oscar has contracted the disease.

What causes ‘hole in the head’ and how can it be prevented?

The most common cause is nutrition deficiencies. You can easily avoid this gruesome disease by simply following the correct feeding guidelines. The other reason your fish may contract this disease is due to bacteria.

Oscar Fish FAQs

How Long Do Oscar Fish Live?

In captivity, most Oscar fish live 8-12 years, but with the correct care they can live up to 15-20 years.

Why Do Oscar Fish Jump Out Of The Tank?

This usually happens when they are exploring their surroundings looking for food. Another possible cause of this is if they are living in a tank that is too small for them. You can prevent this from happening by keeping a lid on your aquarium.


When you take into consideration that Oscar fish are aggressive, very territorial, need specific tank mates, and a carefully planned setup, it’s always best to have a specific tank just for Oscars.

As mentioned previously, Oscar fish are not for beginners, and caring for them may sound like a lot of work, but successfully keeping them can be very rewarding as they are amazing creatures, full of life and personality.