Most people in this area want instant results and i know i have read on alot of these forums of chems have tried a couple of different one"s that you can spray on with X-Jet which i do and rinse with garden hose but i have not gotten great results and sometimes will have to get up on roof to get stubborn areas clean with a little more than garden hose pressure. But forget getting on to a steep roofs with slippery algee and chems was figuring getting a pitchwith (6 nozzle) with a extension wand and ethier do from ridge or from gutter when its needed.