"Wayne Sallee" wrote in message ...
That's not a worm. It's a sea cucumber.

No, it looks like a worm - I have these too in my tanks...

I have identified mine as "spaghetti worm".
They multiply readily and clean the sand from debris.
Very beneficial!

Mine usually sit burowed in the sand, but from time to time
I see one or two in the open traveling -
maybe visiting friends on the opposite side of the tank ;-)

Here is a very nice article about these creatures:
http://www.reefkeeping.com/issues/2002-06/rs/index.php