I have been fighting black algea for about a year. I just found this forum and have been putting nothing in but bleach for the past 3 weeks,about 20 gallons, but before that, just about anything the pool store would sell me. My water before was cloudy and green, now crystal clear but I still have traces of black algea. Will it slowly go away now that chlorine levels are up? Or do I need to shock it some more? The black algea treatment from the pool store seemed to work to cut it down, but I am afraid to put in any more crap.