Use 1/4 cup (60 ml) of Phos-ELIMINATOR PLUS™ for every 50 gallons saltwater or 100 gallons freshwater. Product should be rinsed with freshwater before use. CAUTION – product may generate heat and fizzle upon initial contact with water – handle carefully. Place into a filter bag and put filter bag in area of high water flow. Product is exhausted once you see phosphate levels start to increase.