I have 2 in a 55 and the fight every chance they get, do the PVC pipes reduce the aggression? Mine are WC so they may have a bit more of a mean streak in them.
I havent seen mine fight yet. I had rocks and caves in there but they were always just aroud the corner from each other. The pipes seem to give them more room, and they hang out of it like they do when you see them under a rock or in a mud hole.