Hey Chicki,
In all my tanks i have had feather dusters where in it ( i asumme this is what you are talking about
picture ). If so from what i have found out about them is, and as said earlyer. They are fine, adds bio diversity, they are filter feeders. If you find that they are disturbing the coral then just pull it out from around the corals. The only thing they will really do is bother the coral by growing beside the polyps. (im not to sure about SPS, i have only kept LPS and softies). I have found that my branching hammer and my colt got use to it after a little while.
Cheers!