I have Angela's HC in a Nano Cube with a Damsel. He is quite docile, but I keep him fed. He is about 2 1/2 inches in diameter. I also have about 10-15 hc's im my dispaly tank, 3-4 mantis shimp, 2 pistol shimp, and who knows what else. I have never lost a fish from the predatory crabs and shrimp, that being said I keep my tank well fed. I try to keep a more natural reef, and they are part of a natural reef. The only thing missing is a fish that eats corals, my corals dont grow fast enough to tolerate that, but in nature they keep coral from overgrowing and blocking to much light from itself killing out the base, natural fragging.