strange object in the imperial vortex

[topside]

About four months ago I got a rock with a ton of yellow polyps on it from LFS. Since then I have noticed that a "snail" type animal is on the rock (looks like a small nautilus). It has a narrow spiral shell that is black and white checkerboard pattern(will post pics soon), I have noticed that the yellow polys population is in serious decline, and this thing NEVER leaves this rock. It only comes out once in a while, but never is seen anywhere but this rock with the polyps. Any idea what it is? could it be eating the polyps??

 

[cloak]

Maybe a sundial snail. I've always thought they just fed on zoanthids though.

 

[greenbean36191]

Yellow polyps are zoanthids.

 

[cloak]

Oh yeah.

 

[topside]

It was a sundial snail. That's whats been eating my polyps. I had no idea. That picture is wrong however. They are circular and flat. Not cone shaped. I tries to take a picture of it but my camera won't zoom in that far. I found an old thread (2005) about them here on reef central and it shows many good pictures of this rotten thing. It ate almost a whole colony before i figured it out.