i kept a dwarf with my pair of clowns and multiple other fish that would fit in his mouth, and he never gave them a problem. he lived in a reef tank wiiht plenty of hiding spots, and as long as i fed him, he didnt bother anyone. for 3 months he even tolerated the fire shrimp that perched next to him all day, until i added a cleaner shrimp. within 5 minutes, the cleaner and the fire shrimp were completely eaten. i didnt even see him hit the fire shrimp, i just saw antennas coming out of his mouth. the key is to keeping them fed, so they have no reason to eat anything in the tank. puitting him in last will aslo help out