That's a really pretty bladder snail! Mine are usually as brown as your average pond snail. I'm a fan of them in planted tanks and add them as soon as I set a new one up. I try to keep bladder, pond, Malaysian trumpet and ramshorn going in at least one tank at all times. They keep your leaves clean and glass cleanish and are great algae control if you keep them hungry. Plus they're all pretty good at finding any food should you overfeed. But like AquaAuroa said, if you overfeed with any regularity at all, you'll have a swarm of them. But as long as you don't you won't have that problem. Nothing reproduces past its resources and we provide the resources. They're easy enough to kill off should you ever decide to but I hope that you won't -they're a net benefit to the planted ecosystem.
Nothing good happens fast in an ecosystem.