Mystery snails lay anywhere from 50 to 300 eggs per clutch. A female mystery snail can produce a minimum of three to four clutches per year, even without a mate present. This is because once they mate, female mystery snails can store their mates’ sperm for up to 140 days.
A clutch of mystery snail eggs typically hatches within two to four weeks, producing tiny snail babies the size of a pinhead. When the conditions are ideal, most eggs will hatch properly, so be careful — you might end up with more snails than your tank can sustain.
That said, sometimes mystery snails lay unfertilized eggs as well. An infertile clutch typically has small or deformed eggs with a bad odor.