Atami ATA CalmagProvides a Source of Calcium and Magnesium ATA Calmag delivers a source of two important secondary macronutrients: calcium and magnesium. These two nutrients can usually be found in sufficient quantities in hard water areas, but need to be supplemented in areas with soft water, where the dissolved mineral concentration is lower. As plants progress through the bloom phase, the demand for calcium and magnesium goes up, so most growers can benefit from