​  Gloeocapsa Magma bacteria is what causes black streaks on asphalt shingles, over time it accumulates  as it feeds on moisture and the material of asphalt shingles.  This accumulation begins to show up as black stains. 

This causes damage to your homes roof and if left unchecked this can cost thousands of dollars to replace your homes roof. 

It is also an eye sore and decreases the perceived value of your most valuable investment your home. 

ARMA the Asphalt Roofing Manufacturers Association  recommends a bleach - soap solution be used to safely remove the unsightly black streaks. 

Products sold at Big Box retail stores such as "spray and forget"  can take weeks to work not only that but also walking your roof can be very dangerous if the proper equipment is not used