Sample taken at dusk (87.0 degrees F, just for grins and giggles), showed 1.2 ppm FC. I added 16 oz of cal-hypo, waited an hour, and tested to confirm that I'd raised it by the desired ~ 4 ppm. It came in at 5.4 ppm.

I also brushed it well at about 5:30.

You know, if I'd just gotten rid of the dead algae to begin with, paid attention to the instructions on the cal-hypo bucket, and used that to sanitize the whole time, I probably wouldn't be in this mess. Imagine that - read the instructions! :/