I had an Oscar and a Giant Gourami together in a 125, they didn't get along to well, but they were generally okay together. I got a 240 for them when they both got to be about 12 inches each. I moved them into the 240 and everything was fine, the next day while I was at work they got into a fight so bad that the Gourami knocked the Oscar out of the tank breifly and soaked my nearby computer moniter, killing the monitor. So the Oscar got to stay in the 125 and the GG in the 240. My GG also started be aggressive toward my foot long Synodontis Decorus, so he also resides in the 125. My GG doesn't seem to like anything over a certain size, he pays aboslutely no attention to any smaller fish.