[wetworks]

It is completely impossible to keep pond snails from breeding. You don't even have to have an actual snail- you can become infested just from a single egg. (Though, to be fair, there is never a 'single' egg- more like a hundred!) I fought and fought them in several of my aquariums, and eventually I gave up and have learned to live with them- or at least the ones my assassin snails have not eaten yet. They really don't do any harm, with the exception of clogging up my filters sometimes, and they do not harm my plants or fishes, so I do not militantly hunt and squash them any more. While you cannot keep them from breeding, by watching the amount of excess food that goes into your water you can impose a population limit on them. They will not reproduce enough to overpopulate is their food supply is strictly limited.