Well snails many of which are asexual, will need no help at all in reproducing if you leave them be, and if you have two in a tank, many different species are hempharodites and well.....
YOu get the picutre they'll multiply like crazy, as such is happening in my 55g tank right now, but I have a small algae problem I don't want to scrub and I am letting the snails do the work