D/2 Biological Solution - 1 Quart Bottle (Twin pack)

This is the best of the best. What makes it even better no hazmat gear needed. It cleaned years of black stains off sandstone & even concrete. It may take a few times just leave it & like it says let mother nature take its course. I usually applied it to stains several times prior to a rain. Next time I'm buying a gallon.

I used it to clean a grave stone wiith lichen and moss and it cleared them away with light scrubbing. Worked as promised

Works great!