Resolved Pops out from rock and makes "cob web".

So I can't get a decent pic of it - I tried. It's about the size of a pea or slightly larger. It has a round disc sort of like on the bottom of a snail. The disc raises off the rock a bit and it lets out what looks like a string of cob web. After some junk collects on the string it has a mouth type thing that munched the string back in. If a fish gets too close it slams shut. Don't know what it is but its fun to watch!

 

Hmm sounds like a tube snail, I had a few on this rock that came with my mushrooms. Maybe a variation of them, mine would do the exact same thing, shoot out a web and gather things and then pull it in.

From another forum:
...it's caused by tube snails called vermetid snails. They are common in and on live rocks. The webbing you are describing is their modified antenae which capure food particles in the water and are pulled back to the snail so it can feed.

I have since gotten rid of the rock but the tube snails were def interesting.

 

Thats it! I just googled it and saw pics and that is without a doubt what I have thanks! And K+.

 

Cool, glad to help, have fun with it, I kinda miss mine like underwater spidermen

 

i have a couple of those in my tank as well. I actually got see one of them slowly build its shell thing on a rock. pretty cool.

 

I have one too. Kinda reminds me of the thing in the sand in StarWars return of the Jedi when it is bringing the web back in