The oscar is one of the most commonly kept cichlids in the aquarium. Astronotus ocellatus was first described formally in 1831. Astronotus is derived from the Greek words "astra" meaning ray and "noton" meaning back. Ocellatus is Latin for spotted, referring to the spotted pattern on the body of many wild fish. This spotting can be absent in some wild variants and can certainly be absent in aquarium strains.
The coloration of the "Oscar" can vary from olive-green to gray to chocolate brown in base color with a smattering of some or all of these colors. Black spots surrounded by an orange or red ring on the base of the upper caudal peduncle is a noteworthy characteristic of the Oscar.
The natural diet of oscars consists of smaller fishes, crustaceans, gastropods, and aquatic insects or insect larvae. Although oscars can seem almost "lazy", they are capable of ambushing and capturing fleeing prey over short distances. Oscars in captivity are notorious for their gluttonous diets.
It is very difficult if not impossible to sex Oscars from external characteristics. In the aquarium, pairs have been observed to prepare a breeding area. This is typically a flat stone or slate. Eggs hatch typically in 3 to 4 days. A single spawning may consist of as many as 2000 eggs!
Breeding populations of Oscars in south Florida stem from a deliberate stocking in Dade county by aquarium fish farms in the 1950s. Individual fisherman further spread the Oscar to at least six south Florida counties. Casual observances indicate that the Oscar is becoming less dominant of an invader as once thought.