Ive got garden snails too, I rescued them from my parents house after they where fedup of the snails eating the plants, They used slug pellets to kill them I released them in my garden where they have been living for about a year, The other half wants rid now because they are eating her plants. I collected them all up today and put them in a tank, Ive got about 30 of them.

If a snail does eat a slug pellet it will obviously die, But if you get to it in time there is a way of saving it. A dish full of water, Keep putting the snail in the water, Make sure it can breathe though. It takes between 1 to 12 hours to rehydrate them. IMHO, Its worth it