Can I ask how you caught the thing? I have many hideous visuals in my mind. It looks like it could wr itself around your arm when you grabbed it, and a net does not seem doable. Cool creature, but I am disturbed to think they can live in a tank wothout being noticed.

http://i119.photobucket.com/albums/o...dompics017.jpg

That thing is awesome, kinda reminds me of my centipede.

That was definately a Eunicid worm in your tank, do a search on reefcentral a guy caught one 6ft long that was feeding on his mushrooms. It lived in the pvc pipes he used as a plenum under his sand he took some INSANE pics.