bristle worms, leave it in!IMO
they are great for detritus, and they are cool looking
there is a great varience in the opinion of brisle worms, but the fact is they do eat detritus, when we started, we wanted to oust them too, but later changed our minds, they do help keeping things clean
JUST, PLEEEASE
DO NOT TOUCH
they can be very nasty if touched, if you must remove them please use gloves and/or tongs