I've been getting a lot of good info on this site. I'm getting more perplexed. I am working on a pool for a guy. I believe it is 48,000gal. Yesterday I put in 20gal of chlorine to kill algae. The free chlorine is more than 20ppm as far as I can figure with the cheap Walmart test kit. The local pool store told me my phosphates were very high, and they have a $42 quart to lower it.... I didn't buy it. Last time, I put in 20gal the water went from green to white and was fine until no one put chlorine in the pool for a week. Should I get more chlorine today, or should the 20gal be enough. My friend (the owner) is getting tired of putting money into the pool, and I want it to be as clear as it was. Thanks in advance for any info.