Murderers in my tank

bristel worms and hermit crabs will kill snails I saw a bristel worm crawling up under a snail and he managed to get under its mantel found it dead in the morning when I turned the lights on a bristel worm come out and into the sand. Which means there is not much food left sitting on the bottom of the tank so I don't thisnk I over feed. I have never lost a snail that was on the glass or on a rock. Bristel worms are opitunistic hunters so I think there may have been something wrong with the snail that I saw maybe a hermit attacked it first.

Bill