US Gypsum recommends 2000lbs per ac. I put in 2800lbs in my pond(1 &1/3ac). My pond went from chocolate milk with about 2in visibility to a beautiful clear green with 15in visability in about one month. Check your alkalinity and add ag lime as needed(check previous posts on this subject). Continue to visit this site as it will help you and I can recommend that you subscribe to the magazine.