I'm sure when you saw this title you'd think it'd be a simple answer, but I'm already aware that plants USE oxygen and give off CO2 at night, the reverse of their daytime activity.
My question is this: If my aquarium water is naturally around 7.0-7.1, and with C02 injection is around 6.6-6.8, when it comes to night and my Co2 shuts off, won't the water pH climb back to 7.0-7.1, with surface agitation that turns on during evening hours?
There seems to be a conflict here. Because I try NOT to have agitation during the day so the C02 will stay in the water, but at night to assist with O2 exchange, I have a powerhead that turns on. Now as I understand this is the way to go so plants and fish can get their oxygen at night and C02 can be expelled. However, logic tells me that this is a big fluctuation in pH that is happening every within every dayspan, as C02 is in the tank during day to give a unnatural pH, then leaves it during night, regaining its natural neutral pH.
Could someone explain to me if my thought process here is correct and if this change in pH daily is okay?