Dear hobbyist , bristle worms are beneficial scavengers that eat small bits of uneaten food , detritus ,and dead occupants in the aquarium . They live under and within live rock . Mine come out of the live rock ,whenever they smell the scent of fresh fish . If you don't like them , get an arrow crab , or a coral banded shrimp ,or a bristle worm trap . Bristle worm traps are $10 ,and really work as they contain bait that attracts the bristle worms. The bristle worm trap can also expand in order to trap large bristle worms as well .