I just got back from a 12 day vacation and found the pool in ok shape. It was not green and still had FC =4 after being at shock level when I left it so I added a bit of chlorine to get the FC up a bit. I cleaned the pool and it was looking good. The next morning I looked and the water had a green tent to it. The only thing I had done was to turn the pump off over night after the chlorine was mixed as I did not want to backwash and the flow had diminished some. I had turned on the heater get the temp up some also. Wonder why it went green? Any thoughts? And what should I do now? Take it back to shock level?