Ok question, I got 5 purple mystery snails that were about pea size from my local fish swap and had placed them all in separate tanks. Once they were bigger and started laying eggs I wasn't that worried about removing them because I didn't think mystery snails could breed on their own. But in a few of the tanks I have more babies mystery snails. How could that happen? Was I wrong with thinking there needs to be a male and female snail for the eggs to be fertile?