+1 to mandarinlove from what I have been told. As long as they are not out of control that is. Saw one in my tank and after asking around here decided to let him stay. Then, a week later I bought a 6 Line Wrasse. Haven't seen the worm again and then today, I find out the 6 line likes to eat them. LOL From what I hear, some people pay for bristle worms.