The hippo can be a bit of a bully, but he has been pretty good. The goby likes to grab the hermit crabs and move them into "time out" in the back of the tank. Rock was cycled before it went into the tank. Fish were recommended by the guys that set up the tank. They all seem to be getting along at this time. Have zoas, a toadstool leather, and some mushrooms. Will be a month or two more before I can introduce an anemone and clowns or the other fish that I hope to add. Yes, 12 fish, a bunch of snails, and hermits at the moment. Had three, added the chromis and anthias yesterday.