Need help identifying worm thingy

[gunner105]

I have this piece of live rock that has a hitchhiker apparently i just saw it today came out when i had the lights off as soon as the lights came on it retracted immediately. I watched it for about 5 mins and it seems to stretch itself about a inch just searching the rock for food im assuming anyone have any clue as to what it is

 

[Capt.Nemo]

Tough to see from pic, but my guess is bristle worm. If it has what looks to be little fiberglass hairs all along the sides, then that's your boy.
Don't be alarmed, rumor has it they are beneficial. Unsightly, but beneficial.

 

[gunner105]

Well thank u its really hard to see it just looks like a light gray worm thats stretchy doesnt leave its little hole that ive seen anyways

 

[chefbill]

Peanut work perhaps

 

[gunner105]

maybe, its not that thick i saw 2 more today but they are so hard to see