Opposite pH swings

[Pdandy]

My 265 gallon tank is set up in the lobby at my job. My pH drops during the day down to about 8.1 (sometimes lower) and rises during the night up to about 8.2 (sometimes higher). I have a refugium in my sump that runs an opposite light schedule than the display. Could the fact that there are dozens of people there during the day and no one at night be the reason for this?

 

[Randy Holmes-Farley Verified Community Expert]

Absolutely. The CO2 level in the air from people or other sources has a big impact on reef tank pH. Folks having a big party can see the pH depressed much lower than normal.