Worm ID?

[limitedslip]

I will try and post up a picture, and a video later (my computer isnt cooperating with me at the moment)

anyway, Ive had these on a piece of live rock for awhile. They look like the casings of a small feather duster, but instead of featherdusters coming out, theres lil tenticles come out, and clean up everything. Each case send out one tenticle, and they are placed all over the rock. they seem to be burrowing under hte substrate and poping up in random spots in the substrate as well. Any clue what they could be?