I really enjoy my bladder snails. They did expand in numbers initially, but seems to have settled down to a small group now. I'm careful not to overfeed the tank. The snails zoom up and down the glass so that is fun to watch.
Look like bladder snails, I have them in my tank from plants I bought and put in a alum dip. I went with a 2 hour dip, 2 tablespoons per gallon. But the unseen eggs survived. They stay very small and will not harm plants.