I agree with your math. At full capacity, I'm at ~.2 acres and currently I'm down to ~1/3 of that, so ~2500-3000 square feet, so ~1500-1800 gallons to get 1". Last year it got down below this and I didn't lose any fish, but this year the water temp is probably 3-5 degrees higher and the fish are all one year bigger. Assuming no major fish kill tonight when I get home, I'll try the 1" every other day and see if we can get through it. Thanks everyone for the comments. Wish I had a bigger pond like ya'all!