I'm currently breeding mystery snails. You must have hard water and a tremendous amount of algae. The water level must be under 3 inches from the top because they lay their eggs out of water. They cannot breed without a male and a female. The trigger is to turn the temperature up two degrees. Be patient because the eggs take 2-3 weeks to hatch. The snails will lay 50-200 little pink eggs. You must remove the snails or the eggs before they hatch because the snails will kill the adults (or just really annoy them) A sign of mating is when the male rides on the female's back.