Cal-Mag Plus 2-0-0 is a 100% water-soluble calcium, magnesium, and iron supplement built for hydroponics, coco coir, and reverse-osmosis water — the three growing conditions where calcium and magnesium deficiency is most likely. It supplies 3.2% calcium, 1.2% magnesium, 0.1% EDTA-chelated iron, and 2% nitrogen from nitrate sources.
Calcium supports cell-wall integrity, magnesium sits at the center of every chlorophyll molecule, and the EDTA-chelated iron stays plant-available across the working pH range of hydroponic systems. Because RO and distilled water carry no minerals, and because coco coir naturally binds calcium and magnesium, base fertilizers alone often leave these nutrients short. Cal-Mag Plus fills that gap and is the first component poured in Greenway's 4-part hydroponic feeding program.
Dissolve into a reusable stock concentrate, add it to the reservoir first — before any other nutrient — to help prevent precipitation, then set pH last. Never combine concentrated Cal-Mag directly with concentrated sulfate or phosphate fertilizers; use separate stock tanks and dilute each independently. Adjust the dose to your water hardness, and for coco coir, feed at every watering. Store sealed and dry.
CDFA registered and third-party lab tested for heavy metals, with results consistently well below required limits.