I found this:
As far as reproduction and breeding goes. I would classify these snails as extremely easy. Ramshorns are hermaphroditic, Once fertilized they will remain so for a very long time even without further contact with other mature snails. Even if you only bring one home, the chances are good that it has been fertilized and will reproduce. It takes two to tango originally, but once the tango is danced, it will be a long time before that snail quits producing eggs. Ramshorn lay their eggs underwater on almost any surface. The egg clusters look like a flat amber sheet. Ramshorn eggs always remind me of the onion cells we looked at through the microscope in science class. With a magnifying glass you can see the young snails form and grow inside the eggs. Once developed they will break out of the eggs and more or less disappear into your substrate. They usually come out at night to forage, and will grow fairly rapidly. It has been impossible for me to track time frames from egg laying to hatch to adult size simply because I have too many of these snails going in my tanks to really track one in particular. I do know it?s only a matter of 7-8 weeks from hatch to being large enough to reproduce, if there is abundant food and calcium to promote growth. Ramshorns like most scavengers will reproduce at a rate relative to the available food in a tank. If you have a lot of waste, and a lot of Algae you will have a lot of snails. If you limit waste, Feed conservatively and don?t promote algae growth your population will remain smaller. If the population explodes, and then you clean the tank, you can reduce the population by removing the smaller snails while leaving the largest ones. Since larger snails eat more, there will be less available food per snail and less of a tendency to reproduce as long as the tank stays clean.
)...I shouldn't have to worry about fertilization??
