Let your chlorine drop to "normal" levels but keep it as suggested at around 6 ppm FC or so minimum (at your current 40-50 ppm CYA level) and see if this stuff returns. If it does, then you can try shocking to higher levels (20-25 ppm) as I mentioned in my earlier post.

Richard[/QUOTE]

Hi Richard,
Just checked the chlorine after full day of sun and 80-85 degree weather here in NC.
FC has dropped by 5ppm since this morning. (Remember it held stable overnight at 15ppm)

Is it normal to lose that much chlorine in a day?