Natural Chemistry 4 05131 Spa Swimming Pool Perfect Plus PHOSfree 3L Bottles Combines the proven enzymes of Pool Perfect and the phosphate eliminating power of PHOSfree for a clean and clear pool all season long Pool Perfect works to break down oils and non-living organic material while PHOSfree removes any phosphates that enter the pool water in between treatments Weekly Dosage: 4oz per 8,000 gallons of pool water Includes (4) 3 liter bottles