I don't know, man... saw your video earlier... this thing looks more predatory to me, especially in the way it moves. Doesn't move like a bristle worm.
They're generally considered good, until you pick a frag up with one between your finger and the frag... they do hurt a bit and can cause allergic reactions. Ask me how I know.
I was loosing zoas also, I would find asterinas on top of the polyps. I added a harlequin shrimp and manually removed all the starfish. I haven't lost a single polyp since.