Yeah - you want to get rid of these asap! Left on their own, they'll start eating your leaves and can strip an entire plant! There are a whole host of articles on this issue - google "snails weed soil" ...
There are a number of organic rememdies... sprinkling your soil with diatomaceous earth is one that will work but it will only be effective if kept dry which isn't an option so you'll have to keep re-applying it every time you feed/water... I'm sure there are other things you can do, too... but get on it!
Good luck!