you can keep one in something that isn't your tank just to watch it grow up, i like my little ramshorns really, they're very active little snails, always on the move. i have them in a 3L acrylic box, and change their water every couple of days. they like to eat plec flakes and cucumber.
the only way to stop them coming back is to pull out or kill the ones you see on sight, once they grow big enough they'll lay their own eggs and you end up with hundreds.
chemical treatments to get rid of snails aren't really advised.