What is that little critter attached to the shell of my blue leg hermit crab

[Aseidman]

For some time now, I have noticed a litte white nub (like one side of a clam or a tiny barnicle) on my blue leg hermit crabs. At first I thought it was a growth that kept them from rubbing a hole in their shell since its kind of mounted to the bottom where the shell drags on the liverock.

Surprise, surprise.. yesterday while staring at my tank as I often do, I noticed that the little white nub was lifting up just a bit and that a little black animal was sticking out grabing food of the rocks as the crab moved across the tank....

What is this thing ?

Allen

[Detritivore]

i had a lot of those on my hermit's shell. i dont know if they're good or bad, all they did was pick at the junk on the ground. i think its called a limpet or something like that...its some type of mollusk...i think

[Aseidman]

any more ideas ???