What about the White roofs that I'm starting to see here. They are Blinding white when new. I have cleaned one but was told to just us a mild detergent. Well that cleaned like crap so i just went over it with a floor cleaner and it did well but, I was itching to use a mix with some love but didn't want to damage anything.
I noticed that spots where the water sat for any length of time was Black with growth BUT it had pitted the white roof covering also but only where water was stagnant.
It was about 40,000 sq ft.