You got it. They only seem to bother my zoas from time to time, but I wouldn't be surprised if they help keep them clean. Some of them survived my Bayer, CoralRX dipping so they are very hardy.
Only way to get rid of them is to feed less or manually remove. They are like bristle worms. Their population is controlled based on how much food is avaliable. Heavy feeding = more worms. They don't really bother any of my stuff, but I do hate the way they look!
