Blue Planet Nutrients CalMag with Iron Liquid Supplement Gallon (128 oz) CalMag with Iron supplement is used for plants that require elevated levels of calcium and magnesium to reach their fullest potential and is excellent at preventing and correcting blossom end rot This product helps strengthen cell walls resulting in stronger plant structures and greater overall health Designed for use in all hydroponic systems, aeroponics, coco-coir, all soil-less mediums such as vermiculite, perlite, and in soil Proven results across the internet! See why everyone is raving about Blue Planet Nutrients!