Kelsey Cummings wrote:

Should I be testing for something specific or look at
something more obvious like degraded light output or shifting spectrum
making more favorable conditions for the green hair to grow?

I've read that hair algae requires phosphates. Pick up a phosphate test kit and
check the level; it's probably too high. If the concentration is over 1.0 ppm,
put a phosphate reactor on the system, and your hair algae will disappear. You
will probably have to run the reactor for a few days every few months.

George Patterson
No one ever says "It's only a game." when his team is winning.