My pool was perfectly balanced and overnight it started getting green. I had the pool store test the water and they found nitrates, it tested to a 10 PPM. I drained the 27,000 gallon pool to about a foot of water in the shallow end. I refilled it and let the water circulate overnight. I had them test again and it went down to 5 PPM. They are recommending draining one more time, but said some people can get away with 5 PPM. What is the consensus here? Should I drain it and refill? Or take my chances for the next two months until I close it?