Ok, with triggers, or any aggressive fish, there really isnt any "true" guarantee, per se, but two kinds of snails have made it through a puffer and trigger for me. Margarita snails or mini mexican turbo snails, and some nasarious (spelling) snails but they get eaten a little easier then the margarita snails. Either one is technically food in the wild, but anywho. This is just my opinion, neither lasts forever, but compared to like bigger snails and such, they last much longer. I guess the best thing about the margarita snails is that they are cheap, only about 1.50, compared to like 3 bucks for some other snails. I hope that helps.