yeah. just let them be. almost all bristleworms at detritovors. They jsut eat garbage that is left behind. some will eat corals, but only when they get absolutly huge. im assuming you jsut have the little ones yes? most likely they are good and without them, your levels could go astray. but jsut lowering your nutrient levels will be good for geting rid of them, and depending on how much you have now, for your tank too