Apple snails and mystery snails are both single sex snails and therefore need the opposite sex to mate. If you get just one then there should be no problem with over population. If you do get a male and female the eggs will be laid above the water line and are easily removed. The Pomacea bridgesii will not eat live plant matter however the Pomacea canaliculata will eat live plants. Both will clean up extra food left behind in the tank but they cannot live on just that. They need to be fed veggies such as cucumbers, Kale, collards etc.