I saw the biggest bristleworm ever in my tank last night after feeding some pellet food. He was stretched out along the glass and still had a part of him back under the rock...get this, the part I was able to see was 12" long and was as thick as a pencil even when stretched out! It was gross, but I know he was out doing good for the tank biosphere!
I probably have at least 50-100 of those bristleworms in my tank from the tiny ones in my refugium to the giant in the display.
I have a bunch of those spaghetti worm things in a few of the loose rocks in my tank as well.