Just maybe, try to find out what food source they live off.. 🙂 And reduce this, than they die out and reduce numbers on their own. So it migt just be, that you yourself are the best trap with taking the proper action maintaining the tank.. If despite all it is the tank itself producing the food source and you can do little about it, than it will sustain as much snails as it can. Than it would be unfair to say it is a pest and you might just run into other issues you do not have right now with all the snails present. Because if you remove the snails you probably still have the source they use to live off untouched in the tank with all that this implies..