Ph controlled co2 hasnt shut off

[Philly33]

Unless it's just coincidence but while watching tv tonight i've observed that my co2 is still running. I do understand the concept of a ph set point and controller to keep co2 / ph levels stable. What I'm not understanding is that I thought ph rises during lights on (photosynthesis) and lowers when lights out. So at some point tonight the co2 should stop, correct?

 

[Mebbid]

Unless it's just coincidence but while watching tv tonight i've observed that my co2 is still running. I do understand the concept of a ph set point and controller to keep co2 / ph levels stable. What I'm not understanding is that I thought ph rises during lights on (photosynthesis) and lowers when lights out. So at some point tonight the co2 should stop, correct?

Well, I would imagine that depends entirely on how your pH is fluctuating during the day. If it's not dropping low enough the controller won't shut it off.

 

[aqua_chem]

You pH decreases when the CO2 is on and increases at night when the CO2 is on. Photosynthesis is a basifying process, but your water is probably buffered enough that it's negligible.

What's your pH at and what's your pH set point? When was the last time you calibrated your probe?