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Scientific Name: Astronotus ocellatus

Type: Freshwater

Size: up to 16" (40cm), over 3 pounds (1.5kg)

Tank Size Needed (Minimum): Long, 75 gallon (283L)

Water pH: 6.0 to 8.0

Water Hardness: Soft to hard (5-20 dH)

Temperature: 72-78°F (22-25°C)

Origin: South America, Amazon River

Social: Does best as the only Oscar or in a pair. Will successfully live with fish that are either too fast or too large for it to eat, including other Cichlids, Clown Loach, Pictus Catfish, Silver Dollars, and Tinfoil Barbs.

Life span: 15+ years

Diet: Omnivore. Prefers live food (worms, crickets and other insects, smaller fish, crayfish), with flake or pellet food as a supplement.

Difficulty Rating: Intermediate to advanced

Comments: The Oscar fish is one of those species that frequently gets returned to the pet store. Beginners buy them without realizing how fast they grow and how big they get. One of the cichlid fish, a juvenile Oscar can grow more than an inch (2.5cm) per month, so it will rapidly outgrow a starter aquarium. However, if you want a very large aquarium, this is an excellent fish to keep in it.

The key to a healthy, happy Oscar is aquarium stability and a varied diet. This fish doesn’t really care exactly what pH, hardness, or temperature its water is, but it needs whatever the levels are to stay that way, not fluctuate every time fresh water is added to the tank. Many people make the mistake of only feeding pellet food or feeder fish, but Oscars require different kinds of food to get all the nutrition they need.

Keeping an Oscar’s tank clean can be difficult, especially if the aquarium is only the minimum size. These fish put out a huge amount of waste every day. A strong filtration system is an absolute must, as are regular water changes. Also, be careful about what kind of decorations are used in an Oscar’s aquarium. These fish are not nimble, so they swim into things. They also like to move things around. Driftwood and smooth rocks won’t scrape Oscars if they bump them, so these are good options for tank furniture.

Though cichlids are typically aggressive and territorial, Oscars are usually only aggressive if they are feeling crowded in an aquarium that is too small, or if they are breeding. Otherwise, this fish is intelligent, rather hardy, and quite a showpiece when it gets big.