From what I've read I'm keeping mine. They eat the junk in the sand. Here's a post from another site. I think if you cut back on your feedings for a few days and maybe a few extra water changes, they will go away.
Unknown Worm (A Cirratulid Polychaete I Believe) - 04/20/06
Bob,
<<EricR here>>
First off thanks again for the advice with my tank, I've done a few extra water changes and everything seems to be running perfectly fine. I mentioned in my last email that I was going to try to get a few pictures of this worm I've found to maybe come to a better conclusion as to its species. I think I might have seen it before when reading the sites on your site, but I can't seem to find it again. Either way here are 3 pictures of this awkward looking worm. Looks to me like maybe he needs a good barber.
<<Mmm, your comment is more intuitive than you probably realize. What you have here looks to be a Cirratulid polychaete worm...commonly referred to as a "Hair" worm...often confused with/misidentified as a "Spaghetti" worm (a Terebellid polychaete).
What do you think?
<<A beneficial detritivore...I'd keep it <grin> >>
Thanks again,
Anthony
<<Quite welcome, EricR>>