You remind me of a comment on YouTube to one of my videos where my largest smashing stomatopod (The Juggernaut - O.scyllarus - Peacock) takes it to a very large Hermit crab (shell about the size of 2 tennis balls...Naw don't be mean to the hermits - I like them. I just point and laugh at anyone that adds them to the tank without realising that they eat anything they can pick up and put in their mouth :D
Fortunately, some fish such as Copperband butterfly fish, seem to eat them, and some hermit crabs will eat them as well. Eating these worm snails may well be the only truly beneficial effect of hermit crabs in aquaria.