Roof Maxx’s main ingredient has a natural fungicide in it that will help to inhibit moss and algae growth. Roof Maxx will not remove existing moss/algae/mildew (black streaking) from the roof. We suggest that homeowners schedule a roof cleaning service prior to treating with Roof Maxx. For homeowners who prefer to take care of the cleaning themselves, we recommend the use of Spray and Forget or Wet and Forget. These can be found at most stores like Home Depot or Lowes.