ID This

[RealmTech]

I have these worms that come out of my rock and sand. They have two tentacle like arms coming out of their tube of sand.

Is there anything that eats them?

[Zappo]

I forget the name but it's a very common hitchhiker and they'll help (in a small way) to keep your sand clean. Unless they're growing out of control, they're a good thing. If they are growing out of control, you probably have too much food laying around on the rocks and sand and just cutting back a bit should curb their numbers.

EDIT: Fount it! Chaetopterid or Spionid worms. Apparently you can't tell them apart without removing the worm from the tube. No idea what might eat them.

[mutateddogbone]

stringy things are spagetti worms, completely harmless and great cleaners
tube thingy looks like vermatid snails, also harmless filter feeders but will release stringy net when food is in the water

[Ron Cote]

I have always had a number of them growing in my 120g and they have really never been a problem. Good Luck!