Astronotus: Greek, astra = ray + Greek, noton = back
Anyone who has ever kept an oscar will know that they are very individual, very intelligent and have loads of personality. In the aquarium they can be quite destructive towards decor, plants and equipment due to their nature, size and strength. Their aquarium needs careful preparation to make it 'oscar proof' before adding these fish. Try to use an external filter with inbuilt heating because heater in the usual glass tube are very much at risk in the aquarium itself. Make sure that the decor is robust and fixed so that it can't be moved and use a substantial aquarium hood which can't be dislodged. This preparation will pay off when the fish has grown up. Oscars will co-exist with other large robust fish but generally it is better to keep a compatible pair in their own aquarium because if (when) they decide to start breeding their tank mates are at risk of being injured because in the confines of an aquarium it is unlikely they will be able to move far enough away to prevent being attacked.
Oscars will eat almost everything offered. Pelleted food should be avoided because most of it will be ejected from the gills when the fish grinds it up prior to swallowing it and this will quickly reduce water quality. Instead use pieces of fish, worms, insects such as crickets, wax worms, freshly sloughed meal worms, beef heart and other suitably sized frozen food. Oscars will regard any smaller fish as food too but under UK legislation it is illegal to use a live vertebrate as food it is also quite unnecessary. There is nothing natural about dropping a prey item in to a small confined space like an aquarium.
There are no external differences between the sexes of oscars but it is thought that the males grow faster than females.
Oscars normally make exceptionally good parents, the pair will first select a territory which in the wild would be around 3 metres in diameter and they would try to exclude all other fish from this territory. Then the pair will carefully prepare and clean a site where the eggs will be deposited prior to spawning. Once the eggs have been laid the pair will be extremely intolerant of any intruders and the brood will be guarded until the fry become independent or until the pair start a new brood. Oscars may have up to 2,000 fry in a single brood so before breeding them make sure that you know what you are going to do with all those fry.
The wild status of Astronotus ocellatus has not been evaluated and so there is no data regarding the health of wild stocks of this fish.
pH: 6 - 7.8
dGH: 5 to 20
Size: 45 cms, (18 inches)
Min tank size: 675 litres
Difficulty level: Intermediate
Aquarium type: Species
Swimming level: All levels
Origin: South America: Amazon River basin in Peru, Colombia and Brazil; French Guiana. Reported from Argentina. There have been other introductions both accidental and deliberate in other parts of the world including Florida and China.
Habitat: Inhabits quiet shallow waters in slow moving rivers, canals, lakes and ponds
Oscar, Velvet cichlid
Synonyms: Acara compressus, Acara hyposticta, Astronotus ocellatus ocellatus, Astronotus ocellatus zebra, Astronotus orbiculatus, Cychla rubroocellata, Lobotes ocellatus