My cya is at 100 and the pool is as thick with green as pea soup. I am in the process of draining 60 percent of the water to reduce the cya to 40. Soon I will have a 9600 gallon pool of pea soup instead of the original 24,000 gallon. At that point, I cannot use the filter. Should I shock the 9600 gallons to 25ppm (as per the pool calculator) or should I fill the pool, retest and balance the chemicals and shock from there?? All help most appreciated and much needed.