its about 5" at the moment, when i put it in it and the firemouth had a bit of a power struggle (gt won) but it backs off when the sev of about the same size goes near it!What size is it? IME, GT's, particularly males turn very aggressive around 6-8" and will do its very best to make the tank its own. I had a male at 6" take over the tank and terrify a large male severum. On the other hand, a female I had wasnt any bother to anyone, occassionally took a dislike to the geophagus, but nothing beyond a bit of chasing.