hitchhicker that has fishingline?

[MikeP]

I agree, sounds like vermitid snails. I have some too. The small ones aren't much to worry about but the bigger ones, depending on where they are, can irritate corals. I had one on the skeleton of my red open brain that caused some tissue damage from the string it shoots out and retracts (thats how they eat).

HTH

[draco]

All I can see is the fishline

[Ephraim]

I have several of the same in my tank. The thread that they "cast" is thicker at the end, kinda fuzzy. Never seen the animal itself, the line just comes out of holes in the rock. All they do all day is cast, reel in, cast, reel in...

[Quagmire]

If it looks like a white thread,Goolge DIGITATE HYDROIDS. Maybe thats what they are.Heres a picture.Right beside where it says click on thumbnail

http://www.melevsreef.com/id/kritter1.html