Yes .... bristle worm. Have heard of people trying to get rid of them, but general consensus seems to be that they are good and the more the better. I have hundreds in both my 75 and 100 gal. and ther is virtually no sign of fish poop on the sandbed. If you don't want it coral banded shrimp are said to eat them. Search for bristle worm on SWF and you will get a list of predators that eat them.