Snail ID?

[premilove]

i found this on one of my zoa frags. i am afraid hes going to eat 'em up! but, i haven't found any missing heads..any idea? my first thought was sundial shell, but the shell on his back is not really in the same format meaning shape of the sundial snail, just similar pattern..he eats algae, i see him on the glass all the time, otherwise hes in the sand..in the sump he goes? or is he safe? or toilet grave?

 

[joe____17]

Looks like a limpet. Beneficial.

 

[premilove]

hey thanks for the reply man. good thing i didnt flush him! he's pretty cool, i saw him earlier come out of my sand like a submarine.