Nerite snails are my snail of choice. They come in a variety of patterns (see aquabid), and they can't reproduce in fresh water. What you get is all you'll get forever! 
They also eat algae, which is rather nice. Just be sure to drop in some weighted zucchini if your tank doesn't produce algae for them to feed on.
Another big thing for me is they don't eat plants
I am not sure if you plan on planting your sorority tank, but if so it makes these guys even better. Lots of other kinds of snails may eat plants.
They also eat algae, which is rather nice. Just be sure to drop in some weighted zucchini if your tank doesn't produce algae for them to feed on.
Another big thing for me is they don't eat plants