After some really high FC usage during the day (around 8 ppm) and no significant FC loss on an OCLT I'm questioning my CYA testing.
This video says 'back to the sun' but is shown opposite. Should the test tube be in the sun or in my shadow? It makes a difference when testing.
Granted it's really sunny and hot here lately, but this is making me think my CYA is much lower than I think.