Tips And Facts About The Oscar Fish

The oscar fish is a unique-looking freshwater fish indigenous to South America. They are also known by their scientific name astronotus ocellatus and by more common names including velvet cichlid, marble cichlid and tiger oscar due to their coloring. Although the South American tropics are where the oscar fish naturally resides, they can be found in other countries including India, China and the US.

Over the years, the oscar fish has become quite a popular freshwater fish for home aquariums due to their one-of-a-kind appearance. It’s easy to be taken in by their appealing looks, the oscar fish can be dangerous to their tank mates. For this reason, we suggest only more seasoned aquarists handle the oscar fish. Other than their capriciousness, the oscar fish is quite easy to take care of and are even more beautiful to look at.

Information ChartOscar Fish
Care Level: Moderate
Temperament: Aggressive
Color: Various colors
Lifespan: 20 years maximum
Size: 12 inches long (1ft)
Family Cichlidae
Diet: Omnivore
Minimum Tank Size: 55-gallon tank
Temperature: 74-81 ºF
Water Conditions: A relatively neutral pH between 6-8
Tank Mate Compatibility Larger fish

Care Level

The oscar fish is easy to care for if it is the sole inhabitant of the fish tank. Being omnivorous, they tolerate a wide selection of food and can be very easy to feed. This species is an intelligent fish with very interesting personalities. One thing is for sure, home aquariums with an oscar fish will never be dull.

How much does an oscar fish cost? They are usually seen in fish stores for about $10 apiece. The price can vary depending on the variety. Since oscars are from a very diverse natural environment, they can adapt to many conditions in the tank. A healthy individual can live a very long life of up to 20 years!

Oscar Fish Care

Temperament and Behavior

Are oscars aggressive? Yes, they are aggressive and territorial marine animals. If one is kept with other fish, you would need to make sure the fish tank gives them enough space to reduce territorial aggression. They are brave fish that aren’t afraid to get into an altercation with its tank mates. What’s worse, come feeding and breeding time the oscar fish can get even more hostile.

They are free-roaming fish that like to swim about the entire aquarium but spend most of the time around mid-tank. Not only are they aggressive towards other inhabitants, but they take out their temper on substrate and decorations too. You may also see them uprooting the plant life in search of food.

The bottom line is that oscar fish have a difficult time getting along with other fish. However, if the right tank mates and tank setup, you could minimize these unwanted behaviors but more on that later.

Oscar fish (Astronotus ocellatus). Tropical freshwater fish.


There are a variety of oscars available on the market and their diversity contributes to their differing appearance. In general, all oscar fish grow to be quite large. They have a oval-shaped body and unique markings depending on the species. They have erect fins with a caudal fin that is fan-shaped like many other cichlids. Sexing the cichlids is near impossible until breeding time.


How big do oscars get? Oscars can grow up to 12 inches (1ft). It takes them about one year to get up to their maximum size, growing about an inch a month.


The color varies and depends greatly on the type of oscar fish. They are really a beautiful species that can exhibit a wide array of colors. Let’s look at the a few of the most popular kinds of oscar fish in more detail.

Tiger Oscar – The tiger oscar has coloration that you can imagine due to their name. They are a common variation of the oscar fish and are very popular as well. The tiger oscar possesses black bodies with orange markings, similar to their namesake and the “stripes” can reach all over their bodies and even to their tails. Tiger oscars can sometimes even reach 15 inches in length in the wild.

Albino Oscar – The albino oscar looks like any other species of albino and are almost entirely white. Some albino oscar fish have red or dark orange stripes along the side of its body. How concentrated these markings are are dependent on albino oscar.

Red Oscar – The red oscar fish takes beauty to a whole other level. They are made up of two main colors, red and black and the intensity of the red hue varies from fish to fish. The two distinct colors are very apparent on the red oscar and they blend seamlessly into each other.

Blue Oscar – The blue oscar can rival the beauty of the red oscar with its cool-toned pigments. They feature many shades of blue on their bodies with some yellow or even pink markings.

Black Oscar – The black oscar fish, as you can probably guess, is mainly black in color. They might features some different colored patches and stripes that resemble the pattern on the tiger oscar, and are mainly made up of shades of orange and red.

White Oscar – Another oscar fish named after a color, you can guess that this shade is its base color. The white oscar fish is completely white with a pinkish tone throughout their bodies. They are similar to the albino oscars but have lost the red coloring.

Green Oscar – The green oscar fish look quite exotic, almost like they belong in a swamp. Their mossy green shade can see some subtle patterns of black and yellow as well


Oscars can live for quite long – up to 20 years! The key to their longevity is oscar fish care. You need to make sure the tank conditions are just so and its tank mates are good neighbors. Their diet and feeding habits will also greatly impact their lifespan.


Their dietary habits and fish food they tolerate makes feeding the oscar fish easier than most. They are omnivorous, which means they require a mix of both greens and meat for a balanced diet. This could take more effort and care on your part, but oscars will eat most things you drop into the tank.

It’s always best to simulate their natural environment when planning the tank setup, and this holds true for their diet as well. In the wold oscar fish mainly feed on insects and crustaceans for their meat source. They also do have the occasional small fish, and larvae and they focus on plant debris for their greens.

Since their diet is so varied, it can be hard to give them what they need in the tank. A good source of nutrients would be fish flakes or pellets. While they aren’t 100% natural like what they would get in their natural environments, the flakes and pellets are engineered to provide all the nutrients a fish needs. There are even breed-specific fish food you can look into as well.

Omnivores need variety so keep your fridge stocked with live and frozen options too. Oscars will love the occasional bloodworm and brine shrimp. As for veggies and fiber, blanched vegetables such as spinach and lettuce will do. The variation in their meals will keep them interested and balance all their needs.

Oscars are quite big, so they would need to be fed 2-3 times a day. The amount will vary depending on their life stage, how many oscars you have, etc. The rule of thumb when feeding any fish is to give just enough for them to consume all of it within a few minutes. After that, any leftovers will be considered extra and should be removed from the tank.

Remember that oscar fish get aggressive during feeding time so it could be better to satiate their stomachs first.


The oscar fish is from the cichlidae family, as all cichlids are. They are freshwater fish native to South America and are very popular in the aquarium trade.

Tank Conditions

Now you know how to feed them, let’s take a closer look at how to maintain tank conditions. For the setup, you shouldn’t use a rough substrate since oscars like to dig in search of food, this could easily injure them. Fine-grained sand would be the best choice. Also, make sure you have plenty of decorations around the tank. Make use of the space by rocks and caves around the tank.

Whatever you place in the tank, decorations and plant life alike, you will need to secure firmly. Oscars love to dig when scavenging for food and they can easily dislodge or uproot objects in the tank.


Since they are native to tropical South American waters, the oscar fish likes warm temperatures with a more neutral pH. The temperature should be anywhere between 74-81 degrees Fahrenheit (23-27 degrees Celsius) and a relatively neutral pH between 6-8. If you live in a colder climate, a water heater can help maintain the temperature and an aquarium light can be useful as well.

Water Conditions

Other than keeping the water at the optimal temperature, you should also make sure there is adequate water flow. In the wild, oscars are used to a stronger current so being able to reflect that in the tank will provide them with more comfort.

Oscars are extra sensitive to fluctuations in ammonia levels. To combat this, you would need to get a good filtration system. Since they can be pretty messy, a filter with added biofiltration features would be the best option. Knowing that they are particularly sensitive to water fluctuations, you should pay attention to chlorine levels as well. Chlorine is an injected chemical in our water stream to kill certain bacteria.

While in small amounts it’s not very harmful to humans, even the minuscule amount we find in municipal water sources can be harmful to animals. This is especially detrimental to fish if there are high levels of ammonia in the tank. The way around this is to use a dechlorinator before you add regular tap water to the tank. A good way to know if you are within optimized parameters is to use a test kit. In fact, you should look into separate test kits for ammonia, nitirite, nitrate and chlorine.

Minimum Tank Size

Since they can get quite big, we recommend a 55 gallon tank for a single oscar fish. If you are planning to have more than one, think about doubling the 55 gallon tank to over 100. Made sure your oscar fish has sufficient space or they could be even more prone to aggressive behavior.

Maintenance and Care

They can be quite hardy and adapt to their environment, but oscar fish care can be quite difficult. For example, their large size dictates that they produce more waste. More waste means more tank cleaning on your part. Of course, you can get feeder fish as a tank mate. A feeder fish will help clean up the debris and algae by consuming them. This will help maintain the tank conditions, even if it’s just a little bit.

The most important job is still up to you. Be prepared to cycle your tank at least once a week. This will greatly decrease the chances of your oscars getting sick as well. Oscar fish are susceptible to a unique illness referred to as “hole in the head” disease. It sounds quite humorous and seems to be very literally named. A symptom of hole in the head is when holes and lesions appear on the head of the fish. Hole in the head can affect fresh and saltwater fish.

Hole in the head sounds funny, but is actually a very serious issue. Other than giving oscars a literal hole in the head and lesions, it is also known to be fatal. The parasite Hexamita is behind this disease and can manifest in the form of other symptons as well including loss of color in the oscars, a loss of appetite and irregular white feces. In order to guarantee this illness isn’t the end of your fish, constant monitoring and diagnosis early on are the keys.

There are also other diseases such as parasitic infections of the gills that oscar fish can suffer from but all illnesses and diseases come down to oscar fish care. You need to make sure they are getting sufficient nutrients in their diet and also keep their tank environment at optimal levels.

Oscar Fish Tank Mates

Suitable Tank Mates

What kind of fish can live with oscars? Well, we know oscar fish are not the best tank mates. They are not only messy, but they can get pretty mean and territorial. Who wants to live with someone like that? Infamous for their aggression, the oscar fish can scare other fish away.

Oscar fish are no strangers to different species, since their natural habitat is full of biodiversity. Due to these conditions, you may think the oscar should be a great tank mate but it only works with the right tank size. No matter what fish, the right tank size can greatly reduce aggressive encounters especially if the fish are territorial.

It’s recommended to keep only one oscar fish as just one should be enough of a handful. To ensure that there won’t be as many breakouts, look into an oscar fish only aquarium.

If you do want a community tank, then look for larger fish that are passive in nature. Passive doesn’t mean meek, we want strong breeds that aren’t antagonists. Such species include other cichlids, arowanas, and more. Definitely steer clear of smaller fish and invertebrates for tank mates.


How many oscar fish can stay together? Oscars do well together and is also the best choice in tank mates. Pairing many oscars together can make for a very exotic and intriguing tank. If you plan on keeping them together, make sure your oscars have enough room. Adding 20-30 gallons to your 55 gallon tank each time you add an oscar will give your oscars enough space to thrive.


Unfortunately, not only can oscar fish care be difficult, the breeding of this species proves to be even tougher. This makes breeding in captivity a near-impossible feat. If at all possible, purchase bonded pairs in the fish store if you plan to breed oscars. This fish can be very picky when it comes to choosing a mate, so it’s entirely possible for you to have a male and female together in captivity and never have them “fall in love”.

Another good way to help them find their true love is to purchase a group of juvenile oscars. This way they will have time to form a bond with another oscar in the group and this could eventually lead to mating. If mating is something you want to conduct sooner rather than later, then the second option could take a lot more time. You would need to wait until they have matured, which could take anywhere between 1 to 2 years.

Breeding is possible however difficult, and the results are the different combinations of oscar fish we see today. Once you have a bonded pair, you can start to adjust the tank conditions to mimic those the oscars are used to for breeding. Since it usually occurs in the rainy season, the temperature needs to be lowered by a few degrees. You wouldn’t do this all at once but instead, cycle the water out little by little.

Since the cooler temperature will mimic the natural climate during these months, it could prompt the oscars to get down to business. You will then need to change the water every day to make sure the conditions are always perfect. You will know breeding is about to begin once the fish start to flare their gills. In a breeding tank, the oscars will find a smooth surface for spawning.

Place plenty of smooth rock surfaces for them to choose from. Once they find on to be suitable, the oscars will clean the surface and the female will lay up to 3000 eggs. Unlike some other fish parents, oscar fish care a great deal about their eggs and will guard them until they are ready to hatch. The female will fan the eggs to make sure they get enough oxygen and the males will keep potential predators at bay.

There is no evidence of oscar fish parents eating their fry, so it’s not necessary to separate the parents from their young as soon as they hatch. You should move them to a different tank before rejoining their parents if you have a community tank. During breeding, the eggs and fry could easily get trapped in the filter. Sponge filters are much safer and can be used for smaller fish as well.

Depending on how many oscars you can, you need to move them to a larger tank as they mature due to their large size. This will ensure they grow to their full size in a happy and healthy environment.


Are oscar fish suitable for you and your tank? If you have an existing community tank, you would need to evaluate the species that are living in there. One thing to keep in mind is the amount of space. Will adding the new fish result in a lack of space, which will lead to aggression and injuries of other inhabitants. You must then check if your existing fish are suitable oscar companions.

They should be around the same size as the oscars or you can kiss your smaller species goodbye. They will be the main source of food and outlet of aggression for your astronotus ocellatus. Will the species in the existing tank thrive under the same water parameters are oscars are used to? The right conditions will lead to healthy and brightly colored fish.

If you are planning to have a tank with just oscars, your job will be infinitely easier. They are interesting fish and very intelligent. One thing is for sure, your new oscar fish will definitely be the main attraction in the tank.

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