Crystal Cube Plus - Phosphate Remover & Clarifier - Twin PackINSTRUCTIONS Ensure chlorine and PH levels are correct Remove plastic wrapper and place one Cube into the sock of the skimmer Weir basket In leafy areas Cube ay be placed below skimmer sock 24 hours after adding Cube backwash filter twice N. B. It is important to backwash filter twice as more dirt than usual will be trapped in filter and pressure may increase dramatically Replenish with fresh Cube every 4 weeks to maintain crystal clear pool water