I'm planning on doing my first all-grain brew tomorrow i've done a lot of planning and researching so I'm hoping all goes well. I'm a bit worried about one thing though, I forgot to get some food grade gypsum for the mash water. I filtered all my water through a brita water filter because my tap water doesn't have the greatest taste in the world and i'm not sure if that would filter out any calcium that might already be present in the water. There isn't a homebrew store in my town and I don't know where else I may be able to get gypsum for brewing. My dad has a bag of gypsum which he adds to the soil in his garden once a year, would that work or is it probably not food grade? Are there any possible subsitutes which are easily accessible which would add the calcium ion to the brew? Ok, one last question, should I even worry about this or will my enzymes do just fine without adding gypsum? Thanks.