Thanks for the info. I will have to order shells when we place the fish order this week sometime.The young hermit will molt several times in a year, while older hermits may only molt once a year or so. They molt because they have outgrown their skelton, which usually means they have also outgrown their shell. It's best to keep a variety of sizes so it can pick the one that fits best. As long as they are larger than the current shell, you should be okay. Having empty shells doesn't guarantee there won't be snail predation, but it certainly can help reduce it... especially at molt time.