the problem with assassin snails is, if you have more than one, they WILL breed worse than the snails you are trying to get rid of. they will lay their eggs, and the juvies will stay under the substrate for roughly 6 months and you will never know. also, they rarely break the water's surface, so if you are trying to rid yourself of terrestrial snails, this isn't a viable option. on the upside, they will eat any aquatic snails, including other assassins if there is no food left. here's the catch, as they breed, then emerge, there's a steady food supply. i would only recommend you use one, if you use any. and for what it's worth, they are less than an inch, so frogs may decide they are a tasty treat. not sure what eating a snail will do to the frog since their shell is made primarily of calcium. i'd be worried more about them getting impacted.