my friend has a 3 year old oscar. its about 11.5 inches. it seems pretty healthy. so the question is can you keep an oscar in a 30 gallon? he said he changes his water 3 times a week 30, 40, 45,30..... the oscar doesnt have any tankmates
it's growth is probably severely stunted. they should be housed in a 55G, MINIMUM and they do best in a 75G. it may be living, but its not living a good life.
I'd say definitly not. It can live as well as you or I can live in a closet...as long as we got food and water I guess we can live - sorta. Would you want to if you were always in a closet?
Even a 55g is pushing it space wise--I've seen the scars on oscars that were raised in a 55g--they had blisters worn on their noses from turning around in such a small area.
I agree that a 55 is too small for most oscars, and even a 75 when they start getting really big (14"+). Personally, I wouldn't get an oscar unless I had a 180 gallon (6'x2'x2') from the start incase I ended up with an 18 inch monster.
If an 11.5 inch Oscar is kept in a 30 gallon tank, it is imperative that a razor blade never be used to scrape the inside of the glass. The fish will grab it and use it to commit suicide in the blink of an eye.
That is not a happy fish, regardless of water change regimen.