You can buy plants that are guaranteed snail free. But you will pay far more for them than you will for the regular sort. They are grown in sealed jars, and are thus much more costly to produce, than pond grown plants are.
Snails are just a fact of life in water.. get used to them, or take whatever measures you feel are needed to get rid of them. Assassin snails are one option, Asolene spixi snails are another pest snail eater, but they'll also go after big snails like Mystery snails. Some of the loaches love snails and eat them eagerly, as do some of the puffer fish.
But they do provide a service. Cleaning glass, eating leftovers and algae too. A few are useful to have. If you see egg masses, usually small clear blobs of gel, remove them to prevent hatching. Pretty easy to scrape off glass, even off some plant leaves.