Spaghetti worms are Polychaetes (bristle worms), just like feather dusters, coco worms, peanut worms, and the ****ey caterpillar looking worms that everyone always calls bristle worms. They are very good to have, because they clean the water and the sand bed. The spaghetti worms clean everything. The only ones that may not be desirable are the latter of the list, only because some of them, though not all, will eat coral. FYI- earthworms are Oligochaetes(oligo=scanty or few, chaete=hair or bristles). Almost any worm from the sea is a type of bristle worm, or Polycheate.