Alum Use to Clean Swimming Pools, Ponds, or Lower Soil pH. 15 lbs @ 2.75 per lb We know a guaranteed method of turning your swimming pool water from green to clean in 24 hours. At 2.75 per pound we have the lowest priced Alum on Amazon. Requires one pound per 1000 gals of pool water. Each order is for 15 pounds of Aluminum Sulfate. We do not recommend using Alum in pools that have Cartridge Filters Aluminum Sulfate can be used to lower soil pH, thus making the soil suitable for acid-loving plants. Our Aluminum Sulfate product is Technical Grade and "Not Food Grade".Our product is not safe to use in Koi Ponds.