I have two black mystery snails in my tank, they are pretty cool to watch! I was wondering how they reproduce. I heard once that they reproduce on their own because they have both sex organs. Is there any truth to this "mystery"?
While many snails are hermaphrodites, Mystery snails are not one of them. They are from the same family as the Apple snail and they are sexed either male or female. You would need a male and female for them to breed but if you have a female, she could be carrying sperm from a previous mating and could still lay fertilized egg sacks in your tank. They lay the egg sacks just above the water line so check under your lid along the top of the tank. You can also read all about them, including how to sex them, at Applesnail.net.