Worm identification

[kmatysek]

Hi, all,
We've got a nocturnal worm and I'd like to know what it is (just 'cause I'm curious) and if it's anything harmful.
We've had all our live rock more than one year, but we just rearranged and have discovered a pretty good-sized worm coming out of one hole. He only comes out at night and is about an eigth to a quarter inch in diameter, at least 2-3" long and mostly black in color. I haven't got a real good look at him as he shuns light, but he may be segmented and I can't tell what the 'head' region looks like, but is not remarkable (no wider than the rest of the body and no obvious appendages). He is always coming out of the same hole in the rock (and I never see the other end) so I'm wondering if he's a rather large tube worm of some sort.
Any ideas?

 

[kmatysek]

Got a better look at it tonight, and it's more grey than black, and the black markings are almost stripes, in some kind of pattern. The head has several tentacles* feelers right on the end which seem to retract into the body as it is retracting back into the rock.

 

[kmatysek]

Hey, Oscar, thanks for looking it up! I looked up some pictures of a peanut worm, but I don't think that's what it is. This seems longer and narrower. Clearly, though, there are lots of species of marine worms, so perhaps it's a little naive of me to think someone could really identify it based on such a vague description. It's just hard to contain my excitement when I discover something new in the tank! I'm especially curious about this one just because he's so hard to see. I bought an astronomy LED light which just arrived, so I'm hoping he'll be more cooperative in red light.
Thanks all for your postings. This sure is fun.