Thanks so much. I'm about at my wits end. I think back to when they first started to appear, (week or so after set up) I thought, "cool little living things already!" Didn't even dawn on me they may be unwanted. Thought they were little feather dusters. Well, my tank is completely infested. There are little ones in the sand and even floating around. Couldn't figure out what was killing the corals. Up most of the night last night reading and trying to figure course of action. Thought of breaking down tank, dry out all rock, then I remembered this morn. they're in the sand! I love my fish, they're so happy. Willing to give up reef to keep them as pets but still, don't even know how to go about that. Thank you for all your help. You've been so gracious. Hope all is well with you and your little pieces of indoor ocean.