the only reason a bristle worm eould go after a clam is because it was dying. so, unless the clams are dead, you shouldn't have any problems. besides, you will NEVER get ris of all the bristle worms.
colarodo reef, aren't you doing the whole clam filter thing?? thats cool. did you get the clams from ffexpress.com? they are having a sale on 3" clams(forgot what kind), 2 for 30bucks! thats a good deal if your doing the filter thing! take it easy!