Phosphate free Powerful formula chelates iron, copper, and other trace minerals Protects against surface staining and water discoloration caused by metals in pool water Protects against calcium and mineral scale buildup 12 Pack Natural Chemistry's Metal Free enables pool and spa owners to eliminate dissolved metals that cause staining of pool surfaces and water discoloration, all without adding phosphates. Metals such as iron, copper, magnesium, and manganese can cause serious staining of pool and spa surfaces, but Metal Free easily removes them no matter the pH level or temperature of your system. Best of all, Metal Free is made by Natural Chemistry, a pioneer in bio-based pool chemicals, allowing you to buy with confidence. Product Dosage Initial Dose: 32 fl oz per 20,000 gallons of water. Routine Maintenance: 4 fl oz per 10,000 gallons of water per week.