what size tank would 2 oscars be ok in I have them in a 55 gallon right now theyre 3 inches I do water changes every 3 days. I have had 2 oscars in a 55 in the past get 10 inches before I gave them to a friend and they were perfectly fine I had no trouble with water condition I did water changes every 3 days. I changed 50 percent of water at a time.