Yep, bleach kills snails. Avalon suggested to me a solution of 1 capful of bleach to 1/2 gal of water and a time of 1 min 30secs for week plants and a little longer for stronger plants. I tried this and it killed allt he planarias, pond snails, ramshorn snails, etc... that I was getting fed up with. My plants took it pretty well, after a few days my guppy grass pretty much died off though, but it did come back, so I'd maybe go a little less on the time or bleach for something like moss.
Funny, just before I saw this thread posted I stumbled across the same seller and saved the link, but I didn't want to comment because I wasn't sure if it was just too good to be true or not. Glad to hear there have been some good experiances with this seller. I may do some business with them in the future.