Can Anyone Identify this?

[josht51o]

Ive had these things in my tank for probably around 7-8 months I noticed them. Seems to be everywhere in the tank and comes out the most at night. Can't seem to find them doing anything bad, atleast that I can see. Just curious what it is. These little white lines kind of seem to come from the rocks as well. They move around when poked or nipped but don't seem to try to harm any animals or corals.

 

[T-J]

Spaghetti worm most likely. Harmless. I consider them good guys, as they clean the sand and rocks of uneaten food.