Indigo halmets are reef safe and are fairly peaceful fish as long as they are not kept with fish smaller than 2 inches (once hamlet is full grown). They will eat small shrimp and crabs, but will general leave everything else alone. Keep it well fed. Unlike other specie of its class, these guys only get 5.5 inches. As long as he is kept with fish around the same size he will do fine in a community tank.