Ramesh NG, CC BY-SA 2.0, via Wikimedia Commons

The Oscar fish, whose scientific name is the astronotus ocellatus belongs to the family of cichlid, and it originates from South American countries such as Ecuador, Brazil, Colombia, and Peru. You are likely to find them in the Amazon River basin and surrounding areas due to this location being one of the most bio-diverse environments on the planet. They prefer living in paces that act as hideouts, such as slow main white waters with the low flow where the predators cannot easily get them. It is among the most known aquarium breeds that is popular for its intelligence and are also known for their aggressiveness. This might come as a shock, especially to the new aquarists as they watch them gracefully swim through the water. For this reason, it is important that you get as much information as possible regarding these fish if you are planning to keep them. They are irresistible due to their vibrant and attractive colors and appearance with amazing personalities. They require a bit of experience to handle them, more so due to their aggressive nature.


Common Name(s)  Oscar Fish, Tiger Oscar, Oscar Cichlid, Velvet Cichlid, Marbled Cichlid, Water Dog
Scientific nameAstronotus ocellatus
OriginSouth America
Temperatures72 to 80 degrees F
Minimum Tank55 gallons
Size 8 to 16 inches
LifespanUp to 20 years
Diet Omnivores
Tank SetupFreshwater
TemperamentAggressive/ Territorial


Oscar Fish is not the best at making friends. In their natural habitat, i.e., in South America, they live in one of the most diverse environments on earth, and that means that they are used to lots of other fish. However, it is about differences in the tank since there is less space, and that is where tension arises. If you want these cichlids, the best instead is to have an Oscar fish-only tank. If you want to turn your tank into a community one ten, you will have to look for some large passive fish that will stay out of the way while also being able to defend themselves.

The tank mates can live in fear due to their aggressive nature, and therefore it is advisable you choose a passive fish. Some of the compatible tankmates include;

  • Jaguar Cichlids
  • Green Terrors
  • Arowanas
  • Jack Dempsey
  • Sailfin Plecos
  • Severum Cichlids
  • Silver Dollars
  • Convict Cichlids
  • Fire mouth Cichlids
  • Bichirs

As you can see, most of the ideal tankmates are fellow cichlids since they can hold their own against an Oscar. Whenever you make an attempt to add any small fish in the tank, it will quickly disappear, and this will be the same case for shrimp and snail too.


Most of the fish can easily be identified using their one main color or minor variations, but for the Oscar fish, they are very diverse when it comes to their color variation and patterns. The solid colors can vary from startling yellow to brilliant red to midnight black. The Albino Oscar fish are also available, but they are rare to find. Some with certain colors are known as the Tigers Oscars due to their adorable little stripes. The red tier Oscars look as if they are magma incarnate with how their red and orange scales contrast with the black scales. The white Oscar resembles the opposite version of the red Oscar with same orange patterns on a background that is white instead.



These fish are distinguished by their bi-colored bodies, and it is one of the iconic variants and the original parental type of Oscar fish. Thye have a velvety texture and a mixture of black and fiery red.


This is one of the most popular Oscar due to their name and distinguished tiger-like patterns.


These Oscars are white in color featuring bright scales, and have a smooth texture. They are not entirely white since you can see reddish or orange in the lower parts of their body. Along with the red and tiger Oscars, they are parental types.


This is a crossbreed variant that has a black body with a tiger-like pattern across their scales and light, pale bands running across.


This is a crossbreed variant, but it should not be mistaken with the Albino. They possess a dull pink pigmentation that blends in so perfectly that it gives them a white look.


This is another crossbreed variant with a yellow gradient over a white body. Despite the fact that they are a little calmer and less aggressive than the rest of the Oscars, they will still feed on anything they can.


This is a rare crossbreed with interesting and intricate patterns. Some greenfish has shades of black and yellow on their bodies. You will also notice yellow-colored circle-like shapes and some with dark green bands and yellow scales.


This type of Oscar can be identified by the contrasting shades of blue on their bodies and patterns that are not seen in other Oscars. You will also notice a blue line as well as brighter shades of blue that really pop out.


They have a longer tail compared to the rest of the Oscars, which usually feature bright orange spots that run all the way up to their head.


This variant originates from Florida, USA, just as the name suggests. Thye is mainly found in places like Miami lakes, Everglades, and Tamiami Trail. They have rings that are orange in color over dark-colored bodies but they resemble the Tiger Oscar fish.


In captivity, the lifespan of an Oscar is very short since there are other factors that can be attributed to the life expectancy in captivity. One of the main reasons why they are not able to live for long in captivity is because of the stress they are subjected to when they are put under the aquarium. The stress can be a result of being unable to move, being confined in one small area, or just being overcrowded by other fish. These conditions are also not suitable for other Oscars to breed or feed well, which generally play a major role in shortening the lifespan of Oscar fish compared to the rest of the tropical fish.


The Oscar fish is a bit different from the rest of the fish due to their appearance and intelligence, and this makes them unique and likable by most aquarists.


All the species from the cichlids are known to be both aggressive and intelligent. Some of the aquarists have reported that their fish usually recognize them, and they will show some exciting behaviors such as wagging their tails and quickly swimming back and forth. Some other owners have reported their Oscar’s amplitude for playing; when they place a ping pong ball in the water, they are known to swim up and interact with the floating ball. This is so uncommon among the fish since most just enjoy watching them, but for the Oscars, you also interact with them.


The Oscars are often described as having a great or big personality. Oftentimes, this simply means your fish does not display simple characteristics and will have a well-rounded idea of what they like or dislike. The personality of the Oscar fish has been likened to that of a dog, whereby they have a love for their owners and are easily excitable. In some cases, they get too excited, and some owners have reported them jumping almost out of the tank.


The Oscars have not been reported to have shown any sign of aggression to their owners, but in some instances, they have shown some aggression when the tank is being cleaned. The aggressive behaviors are demonstrated by opening their mouth as big as they can and flaring their gills so as to look bigger. You should be careful when putting your hand in their tank, especially when they are displaying their behavior.   They may at times bite, but due t the small size of their teeth, it is not dangerous or painful.   If you notice that your Oscar’s are attacking you during the tank clean-up, they may not be accepting the tank mates.


The Oscar fish is a rare fish, and therefore the size of the tank is very critical to put into consideration. For a full-grown Oscar, the ideal tank size should be at least 55 gallons. However, it is recommended a 75-gallon tank or more. If you wish to keep multiple Oscar in one tank, then you should add 20 to 30 gallons per fish you add. For multiple full-grown Oscars, the ideal tank should be 125 gallons or more. The size of the aquarium can be a big deal since they grow to a large size so fast. They are usually sold as young juveniles at the size of one to three inches. They, however, grow at a fast rate than most people would expect. The average growth rate of an Oscar is half an inch every month, and this implies that they will outgrow a small fish within a short period. Most of the new owners are not aware of this, and they are caught off guard without the preparation to house a fish that is almost half a foot in length.

Also, it is important to put into consideration the volume and the shape of the tank. If the tank is so narrow, the fish will have difficulties turning at the end of the tank. It is always important to remember that a full-grown Oscar can be up to 12 inches in length, and therefore, the tank should be able to provide enough room to turn in any direction without bumping at the walls.


Oscars are very active fish. There are many reports that indicate the Oscars are good jumpers, and therefore, they can jump out of the tank if there is no hood in your tank. Therefore, as you set up the tank, ensure that you attach a good and affordable hood. Ensure that the tank is not too heavy or too light in their natural environment when the dead leaves and dust particles are gathered on the surface of water that attracts small fish. That effect is created by moistened tank hood.

When it comes to lighting the tank, you just need standard lighting. There is no need for any special kind of lighting, but adding some extra lights to the tank will cause no harm to the fish. If you decide to add your own lighting, just remember that they need moderate low lighting. This means that your Oscars will become distressed when you leave the light on for any longer than 12 hours. After adding the lighting, keep an eye on the Oscars to see the reaction to it. If you notice that it is affecting them, you can dim the bulb or remove it completely.


The ideal type of substrate is sand and gravel. It’s crucial to always remember that the Oscars love digging as well as taking in the substrate and spitting it out. This can be an issue since it can cause the filter to break. The solution to this s to invest in a prefilter. The function of the prefilter is to trap the debris and particles before the water even reaches the main filter, and this can be of great importance in saving you the cost of damages. To avoid putting too much of the substrate on the floor it should be used sparingly. This is because any  food that has not been consumed and even debris will, over time, sink into the substrate.


The soars are very messy and sensitive to any water changes, and therefore it is important to have a high-quality filtration system to ensure they stay healthy. As a rule, your filtration system should stay strong that is capable of turning the volume of water over four times in an hour. If you want to have the best results, it is good to have both the canister filter as well as a backup hanging on the back.


Plants and decorations are essential in making the Oscars feel safe as they give them a number of options when it comes to hiding spots. Since they can often be found moving small objects around their habitat, it is good to avoid ceramic decorations that are breakable. Also, you should be careful about the plant selection you make. The Oscars have a behavior of destroying actual plants, and this means that they will not last in the tank. Also, they are very clumsy, and they can be seen bumping on things, and for this reason, you should not add any sharp decoration.

 The best option to go for is sturdy decorations, stones, caves, PVC pipes, and fake plants. It is also crucial to avoid adding limestones, coral, or any other calcium carbonates-based minerals as they can affect the level of the PH of the water, and the Oscars are very sensitive to these changes.



Oscars are natives of South America, and they thrive in warm waters. The average temperature of your aquarium should be around 77 degrees F. It should be kept stable, and ideally, it should range between 74- and 81-degrees F.


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


Just as in the case of water flow, it is important to replicate the Ph it would be having in the wild. He waters toxicity can be affected if the ph. the level is not right. This means your Oscars will end up getting ammonia poisoning. Here are some of the key points to note;

  • The ph. should be approximately 7.2
  • The ph. should be stable all the time and stay within the range of 6.0 to8.0.
  • If the ph. is too low, you can increase it using salt and ph and changing kits.


When chlorine is added to water, the bacteria are killed. It is important to note that it is a highly toxic gas that is harmful to fish, amphibians, and mammals. As mentioned in the previous subtopic, ammonia is also dangerous, and therefore when ammonia mix with chlorine, they form a product referred to as Chloramines. This chemical cocktail can cause serious harm to your fish.


When adding water into the tank, it is crucial to always use a DE chlorinator. The role of this is to remove any presence of chlorine and chloramines as well as other metals such as lead. These fish are very sensitive to water changes, and therefore, you should never add the tap water directly into the tank before dechlorinating it. Before going any further, always use the chlorine test kit to measure the quality of water and ensure that all the dangerous components have been removed.


It is always important to replicate the natural diet of the Oscar fish as much as possible. Below are some of the options

Live fish can be fed, but this should not be the only food; you need to supplement it with others.

You can also feed them on insects and worms; they include mealworms and cricket. The best place to get these is from a pet store so as to ensure they have not been exposed to harmful chemicals.

You can also feed them on prepared foods such as pellets, tablets, crisps, and wafers.

Also, they can be fed on frozen foods such as shrimps, scallops, squids, and clams.



These are small fish of around one and a half to three inches, and they should be fed at least twice a day. However, you may need to experiment with this as it is a rough estimate.


When the Oscars reach the size of 4 inches, they are now sub-adults. At this range of 4 to 6 inches, you should still be feeding them daily, but you can alter their schedule, such as feeding them twice today and feeding them once the following day.


The Oscar fish are considered adults after they have reached the length of 7 inches and above, and at this stage, they should be given a very wide assortment of food. At this age, you can feed them every other day, but you should keep monitoring them. If you notice they have become a little chunky, you can adjust the feeding schedule.


Oscars can go for between 2 to 4 weeks without eating. Larger fish can generally go for longer without food. The length of stay depends on the strength of the fish. This means that if you have been feeding them well from a young age, you will have strong adults who can o for long without food. 


 If you are planning to breed your Oscars, it is not an easy thing. They require a great deal of experience in order to breed them successfully. However, that does not mean it is completely not possible to breed them, you can, but it is not easy. One of the main challenges you are likely to face in the process of breeding is how picky they are when it comes to mate selection. This is the main cause of most breeding attempts fail. The solution to this is to buy two Oscars that have already before or those that have grown together. This saves you cost and time.

To create an environment that looks the same as the mating season for the Oscars in their natural habitat, the first step is to lower the temperatures just a little bit. Doing some partial water changes every 2 to 3 days is also another method to encourage mating. If this works, you will notice some behavior change in your Oscars when they are ready to mate. There will be some fins shaking that looks a bit unusual at times. Thye might also open their gills a bit more than normal. If you notice this behavior, that is a good sign, and you should not be worried.

In the breeding tank, you need to ensure they are locks for them to lay eggs on. This is because they prefer laying their eggs on top of rocks. Once they have been laid, the pat will be moving around their eggs until the hatching time. You might sometimes notice the female moving the substrate away to ensure the eggs are clean. After two to three days, the eggs hatch, and you will now need to look for a new home for the juveniles that will help them facilitate their growth. Due to their high growth rate, you will need to be careful so that when they get to a certain size, you will move them to a bigger tank.


The only way to differentiate between male and female Oscars is by the breeding tubes, which only appear right before and during the spawning. The females consist of a breeding tube that is stubby and wide and flat at the end. The males  consist of a breeding tube that is thin and at the end it is pounted. Since they can only be correctly sexed during the breeding season, it is very difficult to go to the pet store and by male and female, especially when they are juveniles. 


Despite the fact that the Oscars are very rate to get sick, there are a few things you need to be aware of as an aquarist. One of the common diseases that can affect the Oscars is the hole in the head. If you notice holes and cavities starting to form across their head, you will know that your fish has contracted the disease. This disease is mainly caused by nutritional deficiencies. To avoid this dangerous disease, you need to follow the correct feeding guidelines. It can also be caused by a bacterium.


How many Oscars can be kept in one gallon?

They are large in size, and they need a tank of at least 55 gallons and an addition of 20 to 30 gallons for every fish you add.

Why do Oscars jump out of the tank?

The Oscars sometimes try to jump out of the tank in an attempt to explore the outside environment and sometimes in search of food. Other times they may try to escape if the tank is too small for them. To stop this, you need to secure the tank by placing a lid at the top of the tank.

Are Oscars freshwater fish?

Oscars are freshwater fish that originates from South America. They prefer living in slow-moving rivers, especially around the Amazon basin.


There is no doubt that Oscars can make the ideal addition to your tank with its friendly deposition and intelligence. You, therefore, need to carefully research them before taking them home. However, if you are looking for a long-time commitment but get rewarded with a friendly fish and intelligent one, then the Oscar fish is the right choice. Its head or tail-wagging behavior is one interesting thing that will always please you. We hope the guide has given you all the necessary information you need on matters to taking care of the Oscar fish.

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