The Water Softener pillow lowers general hardness (gh) and removes hard water mineral deposits and toxic heavy metals from aquarium water. It provides continuous removal of minerals, such as calcium and magnesium and heavy metals (such as calcium, magnesium, iron, copper). Comes in one fully rechargeable 6 1/2" x 6 1/2" pouch. One pouch treats 110 gallons. Place pouch above foam filter pads.