Roger Sherman and the Connecticut Compromise. In Article VI of the Constitution of the United States, the framers declared, This Constitution... to be the supreme Law of the Land..
Copper gutters are very corrosion-resistant, so they will endure even in harsh conditions and areas with a great deal of acid rain. It is also sturdy, and it meshes well with a wide variety of roofing materials, including slate, cedar shakes, and composite roofing.
Once the roof is clean, you can prevent the algae from coming back by installing a 3-inch strip of copper at the top of the roof. Every time it rains, a tiny amount of copper will wash down on the roof. Copper is a natural biocide, and the algae will not grow in its presence.