Hmmm.
I happen to love Stomatella snails. I had a lot before my tank got wiped out in Hurricane Katrina. I also love electric blue hermits and have six large ones. Maybe that's why I haven't seen any Stomatella showing up in my tank apart from one that I saw for a few days and haven't seen lately.
You have first hand experience that this is a preferred prey item of the electric blue Mr. Bill?