[APD] CO2 levels at night question

[Kevin Stringer <kstringer1974 at yahoo_com>]

>>>I run a pH meter connected to a CO2 tank.  From what I've read, I  
expected CO2 to be off when it's dark, but my solenoid clicks on and  
CO2 is injected at night and early in the AM before it's sunny or the  
lights are on.  CO2 on means pH has risen.  Plants use CO2 to fix  
carbon and give off O2.  If it's late at night, with just a little bit  
of light coming from another room, or early in the AM first thing when  
I get up, what's responsible for the CO2 going on?  Any hints?<<<

The PH will naturally rise as CO2 is no longer being injected into the tank and carbonic acid is not pulling down the PH. If you have a calcareous material in your tank like limestone that will also bring your PH back up as soon as the CO2 goes off. But I"m guessing that your natural PH for the tank is being resumed once the CO2 goes off and that the natural PH of the water is higher than your setting to inject the CO2. I don't think that should be a problem for you though as long as your CO2 levels are in the safe range. If you are concerned about that, you could always set up a air pump and air stone on a timer to go on at night, but it's unlikely you really need to do that.

Hope that was helpful.

Cheers,
Kevin R. Stringer
kstringer1974 at yahoo_com


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