Astronotus ocellatus (Oscar) 

Very few species need less to be said. Astronotus ocellatus is one of the most widespread species in freshwater tanks and - along with discus and angelfish - the most common cichlid. Although it grows to over 30 cm (and very quickly, too) still it is not a very aggressive species. This is not to say that it is perfectly suited for the average community tank. The oscar will eat any fish that can fit its mouth without hesitation. While feeding there is no need to offer it feeder goldfish or guppies. Apart from the risk of infection - which is much bigger than most hobbyists think - this may increase the fish's aggression without offering any additional nutritional value. The oscar can be trained to accept any good commercial cichlid food (preferably in sizeable pellets) as well as frozen food or food prepared by you (a mixture of vegetables, shrimps and fish fillet will be really appreciated. It is definitely the entrance to the New World cichlids and can be regarded as the introduction to more aggressive species. The overall behavior of this fish will train the fish hobbyist well enough to keep other similar (but more aggressive) species. The pH is not very critical (anything in the 7-7.5 region will do) but the filtration system must be capable of coping with it - a really greedy eater and a messy fish. Extra care should be taken by the hobbyist not to forget the adult size of this fish since an oscar will outgrow a 20 gallon tank within one year while most petshops will not accept it back at that size.