What is this

[kevin d. lassonde]

please help, came in on my live rock
its reasonobly small, lives in a hole, has a hard cover like the foot of a snail, when open there are 2 arms, when i feed the tank it spits out a thread that snags food then eats it

 

[mr . salty]

I have quite a few of these in both my main tank,and refugium.They don't seem to cause any harm,and don't grow any larger than you have described...I remember once someone saying that they were indeed some kind of snail...But they live in the cracks and holes in rock and substrate...

 

[ocellaris_keeper]

Sounds interesting, can I get one?