I've been thinking about doing a 20 gallon long NPT and figured I would try mmy hand at live plants by floating Ancharanis (spelling?

) and a moss ball in each of my 5 gallon long tanks. Well, I'm glad I did the practice run because my plants each had snails on them. At first it was only 1 or 2 snails so I ignored them because I figured that if I didn't feed them they would just die. Not only is that idea a bit mean but 1 snail turned into 15 in one of my tanks and the other tank now has 20 snails. I'm pretty sure 5 gallon tanks shouldn't have that many snails.
I have no idea how they are thriving since I'm litterally ignoring them in the hopes that they will die off. I have nothing against them and I even think the adult snail is cute. But they multiplied to the point that I'm worried my tank is over stocked already and I haven't even added my betta fish yet. Since they seem to be living off of my live plant, is there a humane way to kill snails?
Also, I have no idea what kind of snail I'm dealing with since it hitch-hiked into my tank.

The adult seems to be about an inch long with a brown shell that I only see in the early morning when I get up at about 6AM and at night.