Well, first make sure that there are at least four hiding places for a 6" fish. Then make sure your aquascape breaks up the sight lines in the tank so that each fish can claim a territory out of sight of the other. I recommend siting the hiding places in zones so that each is in sight of no more than two others. (or, to flip that on it's head, no matter which one the fish is in, there's at least one hiding space he can't see with his head sticking out of the place he's picked.)
Keep melafix on hand. Sooner or later they will fight. RTBS are one of those fish that you should keep one or more than 5.