There are a few good methods. The nutrafin 7 day feeders have the highest calcium levels of all the feeders. Of course, you know about the drops. Another method is to use antlers. If you hunt yourself, or know someone that does, a deer or elk antler piece in the aquarium will provide quite a bit of calcium. I don't like the CC method due to the pH change. I personally just use seachem liquid calcium. I've got thousands of snails, and no problems.