For fun, I ran the app. The lights are off in my low-tech.
There's a time stamp (h:m:s) with the co2 ppm.
Co2 ppm = 10.01
Co2 ppm = 11.05
Co2 ppm = 12.16
Co2 ppm = 12.88
Looks like the trend is the CO2 builds up till the lights turn on. Who knew there was a natural CO2 generator in my tank
.... Actually, I knew.