Do your shingles look black like these? 
This is a silver asphalt roof in Sarasota County FL that is completely covered with black algae stains. This home was cleaned from roof to curb with our soft spray chemical algae stain removal system. The stains on the shingles will take about 24 hours to be completely removed. Once a good FL rain rinses the shingles they will be restored to like new.
Cleaning a roof chemically is like 
spraying your grass for weeds. You want to remove the weeds without damaging the grass and its root system. Spraying too much chemical will burn the grass also and the same is applied with roof cleaning. You shingle acts as the grass (the part we do not want to damage) and has algae blooms (like weeds in your grass). The cleaning solution must be applied in a safe professional manner just like when your lawn is sprayed. The only difference is a shingle roofing system like this one can cost in upwards of eight thousand dollars. Do not allow just anyone to clean your roof!
PEERLESS Roof Cleaning Sarasota FL takes every precaution when providing services. We are used by many major shingle roofing manufacturers for warranty cleaning and always adhere to ARMA roof cleaning Sarasota guidelines.
About Tom Peerless