Wow, as usual this place provides plenty of information. Thanks to everyone for the good input. I may have painted myself into a corner with what fish I can safely add, though, as I started out with what are considered semi-aggressive fish- the Red-lined Wrasse and Orchid Dottyback. I have been fortunate as neither has shown any aggression towards the other and they hang out in the same areas of the tank. In fact, the Wrasse sleeps in the sand right outside the cave that the Dottyback sleeps in. But adding something peaceful like a Firefish at this point may be asking for trouble, although my tank is a good size and there are lots of caves and hiding places in the rock.