Looks like bristleworms. Do some googling to read up on them. Most are harmful and even beneficial. If they are reproducing like crazy it could be a sign of overfeeding. Just be careful not to handle them with your bare sting as their bristles can sting, some pretty bad.
thanks...i goodle them, you guys are correct. i dont bristle worm in my tank. i see to much. si i'm watching how i feed my fish and corals. but how do i get rid of them. sites are saying to use a trap and put food. they must be some fish or invert that will eat them?