I do not add it 24/7.
I can add a lot for the photoperoid rather than a sustained chronic level that is going to be more harmful to fish, bacteria etc and it adds a measure of safety should an over dose occur and also saves on your gas if you use Gas tank CO2.
DIY is easy to do this way as well.
We add CO2 why?
To fertilize the plants, not to control pH, pH is just the measurement to determine the CO2.
You do not need CO2 at night at all.
The fish are not as concerned about the pH as they are about the alkalinity and GH.
FYI, pH changes are enormous in aquatic plant ecosystems, 2-3 units are common in shallow planted lakes, some times 6 to 10 in some cases.
Regards,
Tom Barr