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Care Guide for Oscar Fish – The South American “Water Dog”

Oscar cichlids are one of the most popular fish sold at pet stores because of their beautiful colors and unique personality. These “water puppies” are intelligent enough to recognize you as their owner, will come up to the front of the tank to greet you, and can be trained to eat out of your hand. Also, they can get moody and sulk at the bottom of the aquarium because you altered their environment by doing a water change or moving the decorations. However, many people don’t realize they grow to the length of an American football and can live as long as a dog. Keep reading to learn how to best care for this incredible “wet pet” and see if it’s the right fish for you.

What are Oscar Fish?

Astronotus ocellatus is found in countries all over South America, mostly in slow-moving waters that have tree roots, rock, or other shelter for them to hang around. While you may see juveniles in the pet store at around 2–3 inches (5–8 cm) long, adults usually reach 10–12 inches (25–30 cm) or more. In fact, they often rapidly grow and achieve two-thirds of their adult size within the first 6–12 months. Then development slows for the rest of their 10- to 20-year lifespan.

What are the different kinds of oscar fish? This cichlid comes with big, bubble eyes and an assortment of color variations. The most common type is the tiger oscar with its bold, red-orange markings against a black background. Other varieties include albino, red, lemon, black and white, and long fin.

How much do oscar cichlids cost? They are widely available and easy to breed at fish farms, so we usually see smaller oscars for $7-9 and bigger oscars for $15 or more.

Albino Tiger Oscar - Astronotus ocellatus

This albino oscar is very cute as a juvenile in the pet store but can one day grow to the length of a foot-long hotdog.

How to Set Up an Aquarium for Oscars

Oscars are very hardy and can live in tropical temperatures between 74–80°F (23–27°C) and pH levels of 6–8. As a big fish, they create a lot of waste and need adequate filtration. We have used hang-on-back, canister, internal, and sponge filters with our oscars. The type of filter doesn’t really matter as long as the current is not too fast, it’s able to handle the bioload, and you are able to easily to clean it.

The most frequently asked question we get about their housing is “What size tank do I need for this number of oscars?” While some people say that a 55-gallon tank is the minimum for one oscar, we personally believe 75 gallons (280 L) is better so that they have more swimming space to turn around. For two oscars, look for an aquarium that is 5–6 feet (1.5–1.8 m) in length and holds at least 90–100 gallons (350 L).

How many oscars can you keep together? If you have the space, you can try to put multiple oscars in a monster tank, but you may run into issues where some of them are very territorial or more aggressive than expected. If the situation doesn’t work out, then be prepared to remove some of the fish. For example, we used to keep three oscars in a 125-gallon fish tank, but then two of them formed a pair and bullied the third one. Eventually, the third oscar had to be moved into another tank.

What do oscars like in their tank? Decorations can be a challenge since oscars are very large, powerful fish that like to rearrange their environment and uproot plants. Aim for decorations with no sharp edges so that your oscar won’t be injured if he tries to move them. Also, don’t add too many decorations that can impede their movement and take up valuable swimming space.

oscar fish in aquarium

Use simple decorations with rounded edges that won’t take up too much of the oscar’s swimming space.

What fish can live with oscar cichlids? Obviously, this species has a big mouth that can suck up any fish or invertebrates small enough to fit inside, so do not keep them with nano creatures. Despite their large size though, they are not overly aggressive (except during spawning seasons) and can be picked on by other big fish, so choose their tank mates carefully. We have successfully kept them with bigger, peaceful fish like silver dollars, certain plecos, and other medium-sized South American cichlids.

What do Oscar Cichlids Eat?

These omnivores tend to prefer proteins, but they will opportunistically consume anything edible they can find. In the wild, their diet includes insects, crustaceans, worms, small fish, fruits and nuts that fall into the water, and other vegetation. We like to feed quality fish foods like Xtreme Big Fella Pellets and Hikari Cichlid Excel medium pellets. Freeze-dried krill, crickets, and mealworms are also favorite snacks that they enjoy. Finally, you also give them live snails and earthworms if they are easy to obtain.

Make sure to provide a wide variety of foods and consider adding Vita-Chem supplements to provide all the essential vitamins and minerals they need to avoid health issues like “hole in the head” disease. Plus, oscars are very eager eaters that love to beg for food, even if they are already full, so adjust their portion size so they have a slightly rounded belly that is not too concave or swollen.

tiger oscar cichlid

Large cichlids can be prone to hole-in-the-head disease, so keep their immune system healthy by feeding a varied diet with different kinds of foods.

How to Breed Oscar Fish

Most people do not intentionally breed oscars because females can lay hundreds to thousands of eggs and it’s very hard to find homes for so many large fish. Also, it is difficult to sex oscars because both males and females are nearly indistinguishable in appearance. When the oscars are around 1–1.5 years old, you can try to identify their sex via a technique called venting, which involves flipping the fish on its back and examining the reproductive area. A male has two small holes of the same size, whereas a female has one smaller hole and one larger hole that is the ovipositor (i.e., breeding tube used to lay eggs).

However, even if you identify a male and female, they may be picky and not willing to pair up. Therefore, some people buy a group of six juveniles, wait till they’re old enough to form pairs, and then isolate a chosen pair in their own tank with no other fish. The female lays her eggs on a flat rock or a cleared-out area on the bottom of the tank. Once the male fertilizes the eggs, they both aggressively guard their brood against would-be predators. Once the fry have hatched, move them into a smaller grow-out tank and feed tiny foods like live baby brine shrimp. If you leave them in the same tank, the parents may predate on their own young once they are freely swimming.

pair of red oscar fish

These red oscars have paired up and will fiercely defend their eggs during breeding periods.

If you’re willing to make the commitment, oscars are wonderful fish to keep and will give you many years of enjoyment. Just be aware that bigger fish can be hard to rehome, so make sure you are able to provide for them for the entire duration of their life. For more information on smaller cichlids, check out our favorite species that you can keep in a 29-gallon aquarium.

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