bioguard BioGuard Back Up 21 Quart Pack of 2 Proven Effective Algae Preventative NonStaining Keeps Water Clean and Clear

BioGuard Back Up 2 (1 qt) (2 Pack) One of BioGuard's most popular algae preventatives. Works well in chlorinated and brominated pools. A powerful surfactant/wetting agent makes Back Up able to work in tiny cracks and crevices where algae start. 40% quaternary ammonium based algicide pH 5.7 Highly effective algae preventative and algae killer Keeps pool water clear and free of visible algae Activity increases as water temperature rises (and you need protection the most) Will not affect pH levels Non-staining Suitable for all pool surfaces Use once a week Directions for use: 1. Adjust pH to between 7.2 and 7.6 2. Adjust chlorine residual to 1-4 ppm 3. For initial application, pour 32 fluid ounces directly into pool per 25,000 gallons of water (4ppm) 4. For weekly application intervals, pour 1 fluid ounce directly into pool per 5,000 gallons (0.5ppm) of water weekly. For two week application intervals, pour 2 fluid ounces directly into pool per 5,000 gallons of water (1ppm) every other week. 5. Following heavy rain showers, add an additional 1 fluid ounce per 5,000 gallons of water Vacation Treatment (when away for one week or more) 1. Add 4 fluid ounces of Back Up per 5,000 gallons (2ppm) for every week the pool will be unattended 2. Pour product around the edges of the shallow end if shock is also being applied in the deep end