My pool has been running at 4 ppm FC as maintained by my SWG and about 30 ppm CYA, my pH is 7.3. My pool water has always been crystal clear for almost 2 years and counting, never even a hint of cloudiness or algae in the water. Since early this spring, I've been scrubbing off small spots of green algae from my pebble-sheen mostly in the curve where the wall and floor meet. I've been finding 2 or 3 spots a week that want to grow. If I scrub tham well enough, they don't seem to come back, but new spots show elsewhere. Right now I'm bleach shocking the pool to a little over 15 ppm Cl since we're going away for a few days. After I get back I'll have a pretty good idea whether the shock has any effect on the algae spots returning.

I seem to remember Ben's pages saying somthing to the effect that certain types of algae would grow quite nicely in 5 ppm Cl, and that Shock levels for at least 4 hours were necessary to get rid of them for good.