Unresolved Some sort of tube worm?

Ok so I noticed this little thing had some feelers coming out of it and I couldn't get a picture of the creature, but there is something living in the small tube on the right (left one is empty) of the acro frag. Also noticed some kind of stringy thing attached to the end of the tube, I plan on dipping it tomorrow after work if I don't get good news...

 

Vermetid Snail?

 

Yep, vermetid.

 

Ditto

 

Ok so I'm guessing they aren't a threat?

 

i have a bunch in my tank, they are harmless however, they deploy a slime like trail that can get on your corals and it can look fairly ugly, but they are good filter feeders