Cleaning Drivet on a home

Need recomendation the best way to clean DRI-VIT and remove slight discoloration caused by moss, algae. I believe that soft washing is the correct way . But what chemical should I use.

Softwash with sodium hypochlorite and lots of surfactant. You may need to hit the bad spots with a stronger mix via pumpup or 12v pump. Prewet it and go as light and easy as possible.