By a ton I mean like idk 15-20 in my 10 gallon. I just put a piece of lettuce in and they are all flocking to itIf you actually have a ton of pest snails in this tank one assassin snails won't put a dent in the numbers. They only kill to eat and the pest snails will breed faster than one assassin can eat them. Your best bet is not to over feed the tank and pull them out as you see them.
I could never be comfortable having even one assassin snail in a tank with snails I want to keep. I had to get all the assassins out of my big tank before I put my mystery snails in the tank. I have a lot of them though. Started with a dozen but over the years the number had gone up to at least 100. Probably a lot more than that but I didn't keep track of how many I pulled out.By a ton I mean like idk 15-20 in my 10 gallon. I just put a piece of lettuce in and they are all flocking to it