I have a former customer that has moved to the Harrisburg area. He has a mold/algae problem and I told him I would find him a roofer. If interested let me know.
GKRFG I'm in the Harrisburg area, Carlisle. Algae/mold is a common problem in sections of the area. I can only recommend a company or two but in all honesty, my findings of observing roofs they are always the older gray of color shingles. Zinc strips are recommended at the ridges but it may be worhtwhile replacing the roof. I'm not going to recommend any company knowing that they don't want anything to do with it. Sincerely, PC