Was searching the internet when I found this site. I hope you can help. Bought our house in November and put in a new liner in late winter. all seemed well until the weather turned hot a few weeks ago. It looked like dirt and brushed and vacuumed away easily, but came right back. We even shocked a few times but the yellow/brown areas kept returning to the bottom and walls of the pool. I think this stuff is mustard algae. After reading here a bit, I realize we never got the chlorine levels near high enough to kill the algae. As soon as I finish this question, I am going to order one of the test kits recommended on this site. I don't understand how I will know how much bleach to add or how long I need to sustain the levels way up there during the "slam" to kill the algae for good. Another big concern is what damage will the high sustained chlorine levels do to my new liner? Thanks so much in advance for your help!