Alkalinity matters
Tank alkalinity has been somewhat low but I couldn't figure out why. My calcium reactor was full of media, the CO2 tank was full of gas, everything looked right. That's when I realized I was missing the point, that the pH measurement inside the reactor was not where it belonged. Normally it's between 6.1 to 6.5 depending on my mood, so to speak. The pH controller showed that it was 7.5 and my brain didn't click, that it wasn't 6.5... dumb mental error.