When mustard algae is breeding, you will lose chlorine faster than normal.

1. Operate your filter 24/7.
2. Keep your chlorine in the ORANGE to orange-tinted DARK YELLOW range.
3. Add 2 - 3 cups of DE powder after EACH backwash. That will stop algae from leaking through.
4. Brush the algae spots after each chlorine boost.

Where did you get 53% cal hypo? What *else* is in it? What's the brand/product name?