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Re: [APD] Re: CO2 off at night

John T. Fitch at JTFitch at fitchfamily_com wrote:

>> As for running CO2 24x7, I've always done it. Why? If the CO2 is off at night
>> most will diffuse out of the water by the morning. If you turn on the CO2
>> when the lights come on, it will take a while for it to build up to useful
>> levels and photosynthesis will be hindered in the meantime. And if you have
>> the CO2 running extra hard to make up for this, you are asking for trouble.
>> If you want the benefits of increased O2, why waste half the photoperiod
>> waiting for CO2 to catch up?
> I do not understand this explanation.  It seems to me to be the opposite
> of my understanding of what happens. When the lights go off, the plants
> give off CO2 and the pH drops.

I believe that in most setups the plants alone don't usually produce enough
CO2 at night to keep up with the surface loss of CO2 into the atmosphere.
IOW, the nighttime drop in pH when CO2 is left on is due more to plants not
using CO2 than to plants (and animals) producing excess CO2. I s'pose there
could be exceptions, though.

Dan Dixon

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