Oscars (Astronotus ocellatus) are popular South American fish that have been aquarium favorites for decades. Their popularity stems from their size and color as well as their tendancy to become "tame". They can be very colorful, with brilliant orange markings or flanks. Many variants of Oscar have been developed for the hobby including albinos, reds and even long-finned types. The most important thing to know about these fish is that they grow very large, very fast. How fast they grow depends on water quality, how much you feed your Oscar, and tank size.
Oscars need a large tank to be healthy and happy. Providing a large home from the beginning is much better than continuously moving them from tank to tank. It is not recommended to keep even a single Oscar in a tank smaller than 55 gallons, and some say not smaller than 75 gallons! Keeping them in a smaller tank may stunt their growth, cause deformities, and shorten their lifespan.
Good filtration is essential when keeping Oscars. Their size, large appetites and messy eating habits result in a lot of fish waste. Large power filters or canisters are the best options. Partial water changes (at least 25% every 2-4 weeks) will also help keep the tank cleaner and keep the nitrates to a minimum. Testing the water quality once a week is recommended.
Oscar temperament can vary greatly between individuals. Some Oscars can become very aggressive and territorial, thus they are best kept alone or with other Oscars in a very large tank. Males, in particular, can fight each other for dominance in the aquarium which may lead to injuries or fatalities in your aquarium. If you house multiple Oscars, observe their behavior closely to watch for signs of aggression and take necessary steps to protect the fish. If you try mixing them with other species, consider only other robust fish such as Texas Cichlids or Jack Dempsey cichlids.
Oscars will eat pretty much anything that will fit in their mouth. To keep them healthy it best to feed them a variety of flake, pellet, and frozen foods. Good choices include: Spectrum pellet foods, mysis shrimp, krill, beef heart, bloodworms, and night crawlers. We recommend not feeding live foods as a primary food source for your Oscars. Feeder goldfish can carry parasites and diseases, and are not a complete source of nutrition. Your oscars may appreciate a live treat on occasion, but ghost shimp or mollies may be better options.