Hi,
I'm just learning about how to properly fertilize plants. Seeing as how my water is extremely soft with no KH or GH, I need to add calcium and magnesium besides other fertilizers. I know I can use epsom salts to get magnesium, and baking soda to add carbonates, but what would be a good way to provide calcium? Is regular white chalk pure enough to crush and use? Or are there other easily accessible sources?