Am I understanding the pH cycle correctly?

[ShanePike]

Is this how the pH cycle works?

During the day: Corals and their symbiotic algae (zooxanthellae) utilize photosynthesis to produce energy. This process consumes CO2. The decrease in CO2 makes pH rise.

At night: All organisms in the tank, including corals, respire. Respiration involves breaking down carbohydrates and produces CO2 as a byproduct. The increase in CO2 causes the pH to drop.

 

[Randy Holmes-Farley Verified Community Expert]

Yes, exactly, except #1 can also be done by hair algae, phytoplankton, macroalgae, diatoms, coralline algae, etc.

 

[Garf]

At night: All organisms in the tank, including corals, respire. Respiration involves breaking down carbohydrates and produces CO2 as a byproduct. The increase in CO2 causes the pH to drop

Well, this happens in the day also.

 

[ShanePike]

Well, this happens in the day also.

Does it happen to a greater degree at night?

 

[Randy Holmes-Farley Verified Community Expert]

Does it happen to a greater degree at night?

No. Maybe less if fish and other organisms are less active. It just gets swamped out.

 

[UncommonSense]

Is this how the pH cycle works?

During the day: Corals and their symbiotic algae (zooxanthellae) utilize photosynthesis to produce energy. This process consumes CO2. The decrease in CO2 makes pH rise.

At night: All organisms in the tank, including corals, respire. Respiration involves breaking down carbohydrates and produces CO2 as a byproduct. The increase in CO2 causes the pH to drop.

Keep in mind; most modern homes are so well sealed that the air inside the home can easily exceed 5X atmospheric CO2 levels… this means your tank is likely always exposed to elevated CO2 levels!

The system’s day/night PH is directly correlated to photosynthetic organisms, meaning that PH will drop when there is little to no photosynthetic activity within the system!

Solutions:

- Plumbing your skimmer’s air inlet to atmospheric air.
- installing a CO2 scrubber on your skimmers air inlet.
- installing a macro algae refuge, algae reactor, or algae turf scrubber on a reverse photoperiod from your DT. (my personal favorite!)

Edit: here’s typical atmospheric CO2 a few miles from the Pacific Ocean; in my fish room! — (It can easily climb to well above 2,500ppm CO2 if I spend several hours in there with no ventilation!)