Yes, you do need a big tank, but given that Oscars are not hard to breed, and virtually all the ones you see are captive bred.Originally posted by isaac newton
Hmmm have oscars ever been breeded in captivity???? A friend of mine has a 75 gal tank and that fish is huge! It hardly has any space to swim around.. To breed these fish wouldn't you need a sizeable tank to house these fish and let alone breed them?
Baensch says that Oscars are sexually mature at 4.5", which must help.