Are you sure they're nerites? They look like collonista snails to me. Collonistas get about the size of a BB pellet, and breed in large numbers, like you've described. Have any of yours grown to anything like proper nerite size?
If they're collonistas, they'll be fine. If they're nerites, you'll probably want to rehome some once they grow bigger. I'm sure you can find some takers.