With the SWCG, I've haven't had algae in the water for 3.5 years. I did have green algae start growing in the texture of my pebble this year with the CYA at 30 and the FC at 5ppm. I got rid of this algae by removing phosphates and shocking to 25+ppm (not sure which one did the trick, but happy it's gone.) I went for 3 years w/o shocking, but now I shock whenever we're leaving town for a few days. I just dump in enough bleach to get FC up to 25+PPM, then leave town. I have always returned to a perfect pool. This happens 2 or 3 times a summer and that seems to be about right.