An oscar that seems to almost glow in its aquarium

Oscars are a species of fish that has become increasingly popular in family aquariums. They are native to South America and can be found in the Amazon River basin, where they thrive in warm, shallow waters. Oscars are known for their vibrant colors and playful personalities, making them an ideal choice for those looking for a unique and entertaining pet.

Oscars are part of the Cichlid family, which includes other popular aquarium fish such as angelfish and discus. They are relatively easy to care for and can live up to 15 years with proper care. Oscars are omnivores, meaning they will eat both plant-based and meat-based foods.

Oscars are one of the most popular species of fish for freshwater aquariums. They are often included in larger starter aquariums, and are known for being quite active. They are a type of cichlid fish, originating in rivers in South America’s Amazon. They are known to be aggressive with each other and other fish species.

Because of their aggressive nature the Oscar is usually the first fish for the aquarium. We suggest that you pick its tank mates carefully to avoid having your entire aquarium eaten by your Oscar. This is why it’s generally a bad idea to introduce this fish to an existing aquarium as an afterthought.

They are nocturnal, which means they spend the day sleeping in a sheltered spot, and come out at night to hunt for food. For a family aquarium this could be a bit of a problem, but generally they will be alerted at feeding time by the splashing and movement of other fish in their tank

Though they are more aggressive than other tropical fish, they are still relatively easy to care for, because they are hardy fish and don’t need anything special to survive. When it comes time to feed them, Oscar will eat just about anything you give them, including flakes, frozen food, live food, and even vegetables.

They are very colorful, and have a wide variety of colors and patterns. Even after all of the warnings, many families can’t resist buying an Oscar because their coloring makes them a very attractive addition to almost any tank. 

They are also very hardy and resilient, and will withstand a wide range of conditions without issue. Oscars can be purchased from pet stores, and will cost anywhere from $10-$20 per fish. Less common ones will range from $30 to over $100.

Oscars are very active and playful, making them a great choice for those looking for an interactive pet.

Overall, Oscars make great fish that are both beautiful and entertaining. With proper care, they can provide years of enjoyment and companionship. If you’re looking for a unique and interactive pet, an Oscar might be the perfect choice for you.

Information on Oscars

  • Average Length: 10 – 12 inches
  • Scale Colors: Black, Orange, Red or Lemon (with or without markings)
  • Attention Needs: High
  • Tolerance to Heat and Cold: Yes
  • Good Pet: Yes!
  • Good with Other Oscar: Yes
  • Good with Other fish species: No, they are aggressive
  • Good for Less Experienced Pet Owners: No
  • Health Concerns: Septicemia, Fin Rot, Hole in the Head and White Spot Disease.
  • Average Life Span: 10 to 15 years

Physical Appearance of Oscars

a close up of a yellow oscar swimming with their mouth open

Oscars have long oval-shaped bodies. They have long extended dorsal and anal fins that stretch along their body towards the caudal fin.

Oscars are known to get very long when they are fully grown. Baby Oscars may only be between 1 to 2 inches but they can grow very fast. They can grow an inch every month and may get up to 10 or 12 inches when they are fully grown.

The most commonly found Oscars have irregular markings of black and orange, which are called tiger Oscars. Years of selective breeding have also created many different color variations.

Lemon and red Oscars are other common types. Some Oscars can also have completely solid color bodies with black or white markings on their fins. These markings often have an eye-spot appearance which is called ocelli. Oscars can also be albino, with an all white body with red spots.

The spots or ocelli act as a defense mechanism for Oscars because it confuses the predators. Predators think it’s an eye, which makes it difficult for them to understand which way they will swim.

Baby Oscars and fully-matured Oscars tend to have a slightly different appearance. Baby Oscars have striped bands of orange or white on their body while adults do not.

An interesting feature of their appearance is that they can change colors. There can be several reasons why they might, which will be covered at the end of this article under related questions.

Temperament of Oscars

2 multi color oscars swimming next to each other

Oscars belong to the Cichlid family of fish species which are generally known to be aggressive. Oscars are naturally territorial and can be aggressive with other fish in their tank. They have been known to attack other fish, especially when the Oscars are mating or feeding.

They get along with other Oscars and like to stay in pairs or small groups. We recommend keeping them as a pair, or with as many as 5 together. Avoid keeping three Oscars because two may bond well and one might be left out.

They spend most of their time in the middle to top of their aquarium but may go to the bottom of the tank to look for food.

Oscars are active and are known to uproot plants and other decorations in their tank. All the decorations should be tightly attached to keep your fish from damaging them or moving them around.

Oscars are one of the most intelligent fish species. They seem to sense the surroundings outside their tank and are able to interact with their owners. The Oscars will waggle their tails, fins and heads when they see you approaching the tank. Because of this behavior they are often called “water dogs”.

Best Habitat for Oscars

A tank of around 55 gallons is the minimum size needed for this fish. If you are able to go with a 75 gallon or larger tank it will be better for their health. Water conditions that closely resemble their natural tropical conditions will help keep your Oscars healthy. They are found in slightly warm and slightly acidic to slightly alkaline water.

Tank size

3 to 5 baby Oscar fish can be kept in a small tank of 30 gallons but one fully matured Oscar will need at least 55 gallon tank. For every additional adult Oscar, they will need another 20 gallons. A community fish tank will need to be even larger to accommodate the space the other fish will need.

2 red and black oscars swimming along side of each other


They need a water temperature kept between 75°F and 80°F.

Water Hardness and pH

Oscars need water that is mostly neutral. The pH should be in the range of 6 to 7.5. The water hardness should be between 12 and 15 dH.

Tank Substrate

Oscars are scavengers and like to dig for food, and a soft substrate like sand should be used inside their tank. Avoid using a rough substrate like gravel because it can hurt them when they are digging.


They don’t have any specific lighting needs and any type of regular aquarium lighting will do. Because other fish will usually need a typical daylight cycle we suggest using a timer to control the lighting in the tank to have a regular day and night cycle.


Decorations like plants, rocks and driftwood help replicate their natural environment. Caves can also be added to create hiding places for the Oscars. Keep in mind that these fish can grow very large, up to 12 inches so the size of the decorations like rocks and caves should be added with their full size in mind. By planning for their eventual full size it will save you from the hassle of changing their decorations in the future once they have fully grown. 

An important thing to keep in mind when adding decorations is to firmly attach all of them to the substrate. If you do not do this there is a good chance that your Oscars will uproot them. Not only the decorations, air pumps, water filters or any other tank equipment should be attached as well as possible. Oscars are known to damage things if they are not properly secured.

Tank conditions

The oscar is looking at a new place to live

These are large fish and will generate a lot of waste. It’s important to have a high-quality filtration system that can efficiently clean the waste from the water. A Canister filter is recommended because they are easy to use and also efficient at keeping the water clean.

Tank Maintenance

The tank temperature, alkalinity, pH and level of dissolved organic compounds should be measured daily. Oscars are large and tend to generate a lot more waste than smaller fish.

To keep the level of waste and toxic compounds under control, a water change of 20 to 30% should be performed every other week.

Best Tank Mates for Oscars

There are several things that need to be considered before getting a tank mate for your Oscars. These fish are large and tend to be aggressive. Avoid keeping smaller fish with them because they will chase or eat the smaller fish. We recommend adding fish that are about the same size or large enough that they won’t be eaten by your Oscars. The fish that you add should also be active and ready to compete for food, otherwise your Oscars may chase them away.

Another important thing to look into is the size of the tank. Because both the Oscars and their tank mates are going to be large, a very large tank will be needed. This will make sure all the fish in the tank have enough space for themselves and lessen the chances of fighting between them.

The best tank mates are:

  • Silver Arowanas
  • Blood Parrots
  • Sailfin or Common Plecos
  • Clown Loaches
  • Bichirs
  • Severum
  • Convict Cichlids
  • Silver Dollars
  • Jack Dempsey
  • Giant Gourami

Avoid adding snails and shrimp. Just like the smaller fish species, Oscars will just eat them.

Health Issues

These fish are hardy and generally do not get sick very often. Still they have been known to have the following diseases:

Hole in the Head

Hole in the head (also known as Head and Lateral Line Erosion, or HLLE) is a common problem among many species of freshwater fish, particularly livebearers such as mollies and guppies. It’s a condition that causes lesions on the fish’s head and body, which can lead to infection if left untreated. In severe cases, it can even be fatal. The cause of HLLE is unknown, but it’s thought to be the result of poor water quality and/or improper nutrition.

Hole in the head is most often seen in aquariums with high levels of nitrate and ammonia, as well as a lack of vitamins and minerals. It generally begins as small pits or lesions on a fish’s head and lateral line (the line of scales along the midline of a fish’s body), which can then progress to larger lesions, ulcers, and eventually death if left untreated. It’s important to act quickly when you notice signs of HLLE in your aquarium, because it will only get worse with time.

Fin Rot

Fin Rot is a common illness caused by bacteria in an aquarium. It’s associated with the deterioration of a fish’s fins, scales and skin. The affected areas can become discolored, frayed or disintegrate entirely. In extreme cases, fin rot can be fatal to a fish if left untreated.

The most common cause of fin rot is poor water quality. Bacterial growth can happen when ammonia and nitrite levels become too high, or PH levels become imbalanced. Overcrowding in the aquarium can also lead to fin rot, because poor water quality is more likely when there are too many fish in a tank.

In order to prevent fin rot, it’s important to maintain a clean and healthy environment for your fish.


Septicemia is an infectious disease commonly found in freshwater fish. It’s caused by a type of bacteria called Saprolegnia spp, which infects a fish’s skin and fin tissue, leading to bloody patches on their body and gills. The infection can spread quickly if not treated, leading to death.

Symptoms of Freshwater Fish Septicemia

Symptoms of freshwater fish septicemia include:

  • Reddening or skin discoloration
  • Appetite loss
  • Lethargy
  • Bloody patches on their skin and gills

In more severe cases, the infected fish can also suffer from anemia, swelling in their abdomen or head, and labored breathing. If left untreated for a long period of time, septicemia can cause organ failure and death.

Ich or White Spot Disease

Ich Disease, also known as Ichthyophthirius multifiliis or white spot disease, is a common parasitic disease that affects many species of freshwater fish. It’s caused by tiny parasites that attach themselves to the surface of a fish’s skin and gills and feed on them. These parasites appear on your fish as white spots on their body and fins, resulting in distress and discomfort.

The best way to prevent Ich Disease is to maintain a clean and healthy aquarium environment. This means ensuring that temperature, pH, hardness, and other levels remain within the correct range for the fish species being kept. Careful tank mate selection is also important; some fish are more susceptible to Ich than others. If a fish is already infected, quarantine them in a separate tank.

Feeding Oscars

a pile of colorful fish flakes

Oscars are omnivores that feed on a variety of small insects, fish, crustaceans and small amounts of plant debris in their natural environment.

Captive raised Oscars can be fed commercial fish foods like pellets or flakes. These foods will give them most of the nutrients that they need. They can also be given frozen or live food like bloodworms, brine shrimp and daphnia (a type of small crustacean). Whenever possible try to give them live food. This will help them use some of their natural aggression as part of normal hunting behavior. If they can get their aggression out while eating, they should be less aggressive other times.

They need fiber in their diet which can be given to them by feeding them finely chopped kitchen vegetables or algae flakes.

They should be fed 2 to 3 times a day and only what they can finish within a few minutes. Make sure to feed them enough food. If they are not fed enough your Oscars will get aggressive and compete with each other when they are feeding.

Related Questions:

Why do Oscars Change Colors?

Baby Oscars are born with a somewhat dull coloration. As they grow, the coloration on their body becomes brighter. This is one reason for them to change colors and is a gradual and long process. They are also known to change colors depending on their mood. It is difficult to pinpoint the exact color that different moods can cause. Oscars tend to get brighter when they get aggressive or upset. Sometimes the color change can also be caused by poor water conditions or a disease like Ich.

Are Oscars Difficult to Keep for New Fish Tank Owners?

As already discussed, Oscars can get very large and are also quite aggressive. Their size and aggression makes it difficult for new fish tank owners to care for them. Selecting and keeping tank mates for them is also not easy. They need a large tank which can make it difficult for new fish tank owners to maintain.

Oscars along with their tank mates will generate a lot of waste. This waste will require more frequent and larger water changes than what is generally required for tanks with smaller fish. We only recommend these large fish to owners that can spend the time to make sure the water quality is maintained.

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Maryna is an animal expert that has had dozens of animals in her life over the years. She has never found an animal that she didn't love immediately. It seems like every year she finds kittens that have been abandoned by their mom and she nurses them to health and finds homes for them. She contributes her vast knowledge about animals and family pets to our website and we're forever grateful to have her working with us. She's also an amazing graphics designer and has designed all of the social media images that we use across all platforms.