ID please?

[tomato clown]

This morning when I looked in my tank I noticed this white tube in with my green polyps, it was about 1/16" and slowly wiggled up and what looked to be it growing or exiting a hole was actually it spitting something out. I'm thinking it spat out waste, but Don't know.
After 11 months now this is the first time I have seen this. I have done a search on different things like tube worms and different hitch-hikers, but haven't been able to find anything similar.
Dan

 

[tomato clown]

nope, it did this
kind-of straightened up then pushed something from inside the tube out. Whatever was pushed out fell and the tube retracted. The stuff that fell out pretty much dissentigrated on its way down.

 

[tomato clown]

ok here we go, it looks similar to this but without the shell. Is this possible? and is it good or bad? I have read that certain coneshell snails will

[hr]
fish, so how would I get rid of it if it is a bad one?