don't know what it is?

[wtp64]

sorry no camera for pic it has about 10 to 15 like tenticles like long small spider web keeps on picking up my sand and pulling it in like trying to make burrow or tube possible some kind of tubeworm or something? oh its on a piece of my live rock is it good or bad? or does anybody knows what it is?

 

[Dubbin1]

Without a picture all you will get it guesses.