NeonR..... Thanks for mentioning the alum! Never would have considered using it, but I'll give it a test run next time if I can find some in the spice section. I know there's trace amounts of alum in my baking powder.
Personally, I don't mind snails since my fish like to HUNT them.
I use potassium permanganate for oxidizing/cleaning plants of other destructive critters. I have several lbs of (KMnO4) now.