We have an undulate in a 300 with several species of fish...Lionfish, damsels, wrasses and also a SFE. They all get along fine and the undulate seems to know who tankmates are versus the feeders we add. Ours has gotten so spoiled that he won't go after feeders anymore, he just sits and waits for us to feed him with the feeding stick! LOL..Its almost like he is thinking, "What me chase food!!..I don't think so!!