Worm...i Think?

[showjyr]

I was going to mount this frag on a larger piece of rock. When I pulled it out of the sand it had these tubes attached. I assume they are home to some type of worm but have yet to see a worm.

I recall reading about a type of worm that lives in the substrate and uses the sand as a tube but have no idea where I read it. Can I get an ID?

 

[1entra]

I cant recall their exact name at this moment in time but I have loads of these under near enough every piece of LR. What you tend to get is either 1 or 2 thin long white tentacles come waving out into the water column. They seem to be harmless and as far as I'm aware they are filter feeders so dont worry about them!