Just bought a 40g tank, bought live rock, and now I am finding worms. two different species so far. One of them appears to be the ever-so-common bristleworm, and I have yet to identify the other. I'm not sure about the length yet, but he is doing a great job of tunneling along the walls of the tank, leaving tunnels behind him. He is half brown and half white. The brown end is segmented and retracts, and the white end has what looks like feelers on it. So far, he is about 2 inches long. Anyone have any ideas what it might be?