Tiny Worms In Live Rock?

[Bettafanatic]

So I have a ten gallon FOWLR that is nearly done cycling. I just added a few more live rocks, and while observing the tank, I noticed something peculiar in one of my live rocks.

It was a little worm. it was cream colored. It's head was just waving around while its other half was in a hole in the rock. When I put my hand in to move the sand a bit it disappeared into its hole.

What is this worm? Is it harmful? Should I remove it?

 

[Evilbass]

can you attached a picture? it could possibly be a feather duster?

 

[Bettafanatic]

I've been trying to get a picture of him, but I haven't seen the worm since he disappeared into his hole. He was cream colored and very small. I'll get a picture as soon as he reappears again