When a roof has copper or galvanized items (vent pipes, exhaust fans,
etc.) protruding from it, shingles below these items will be free of
algae stains because rain washes copper or zinc from the galvanized
items off and kills the algae. Has anyone heard of using a copper or
zinc solution in a hose end sprayer to clean remove the stains? If so,
which chemical, what concentration, and what coverage?

I'm experimenting with more conventional approaches (oxygen bleach,
laundry detergent, and a produce called KrudKutter). All require
multiple applications, "scrubbing" with a broom, and generous rinsing.
There may be other proprietary (expensive) items that are more effective
and easier to use, but for now I'm looking for shortcuts.

Thanks,

Ray