Moss Control
Mix iron sulfate with water in a spray bottle, and apply the solution to the moss. Let it dry for a couple of days, then brush away the loosened moss

However, the use of Zinc powder not only kills the moss on your roof. The run-off process creates a funnel of water that is washed back into the surrounding ecosystems. From there, the microscopic traces of zinc sulfate can work its way into water sources and wildlife, posing a hazard to the natural environment. Oregon State University states it is a toxin to aquatic vertebrates. This procedure is invasive and highly corrosive.

For cleaning your roof, you will need to test a small area with a 1% Ferrous Sulphate solution (ie. 10gms/1L of water). If this does not give the desired effect a stronger solution can be used up to a maximum of 5% Ferrous Sulphate (50gms/1L of water).  If you make it too strong, you may stain the roof – it’s not the end of the world – a spray with oxalic acid will remove the staining, but I’d prefer just to see your roof clear of moss!

https://www.tractorsupply.com/tsc/product/shur-crop-31-iron-sulfate-6015998?store=2400&cid=Google-Shopping&utm_medium=Google&utm_source=Shopping&gad_source=1&gclid=Cj0KCQiA1Km7BhC9ARIsAFZfEIvhEOuXpBenQGxy28-WB7D05ZgbHseE_-R11KRaqPF4WVeWYdu3euwaAjyvEALw_wcB