I have about 2 assassin snails in my tank and they're lazy. LOL!
I dont know why, but I feel like I have the SAME amount of pond snails every time I check.
I do see about one empty shell each day.
So I'm guessing they eat one pond snail each day.. or so.
I was really disappointed cuz I heard they were great... you should probably get about 5 or more for each tank.
My assassin snails do not even touch my MTS.. so i dont know.
If you get some diligent assassin snails, i'm pretty sure you'd only need one.