What the heck is this thing?

[hillbillyreefer]

I'm not sure how to describe this worm type thing that came out of my LR today. Worm like about 2" to 3" long 1/4"wide, flat, white, hundreds of legs that look hair like. Crawled out of a hole in the rock looked around for a while then went back in. Couldn't get a picture. Anyone have an idea what the heck it may be, good or bad?

First reef tank, I'm kinda like a nervous parent.

Brad