Hi Jim,

The picture would have to show more (and crisper) detail to be sure
but your worm appears to be a Cirratulid or "Hair" worm. These guys
are beneficial detrivores.

You can find a good deal more information about Cirratulid and
Terebellid worms in aquaria he
http://www.reefkeeping.com/issues/2002-06/rs/index.php


Vermicularly yours,

Alex