I wanted one or two snails for my aquarium. I went to a pet store who told me that the "pest" snails that come attached to aquatic plants were free. While I only wanted 1 snail, she gave me 6 tiny babies! No, I don't want to overrun my tank with snails, so how can I calculate the odds of femailes versus male snails? Of course I can just look for and destroy snail eggs, but I'd like to know the math behind the snails.odds of