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Re: [APD] Re: CO2 off at night

> Date: Thu, 11 Sep 2003 08:28:43 -0600
> From: gbooth at frii_com
> Subject: [APD] Re: CO2 off at night
> To: aquatic-plants at actwin_com
> 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
> 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
> 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.  If the CO2 is left on continuously, the pH
will drop even further. When the lights come back on, the plants start
using CO2 and the pH rises.  So you do not have to *add* CO2 until the
plants have used enough of what is already available to lower the supply
and raise the pH level.  This may take several hours.  At that point, if
you have a pH probe and controller, the CO2 is turned on to keep the pH
(and hence the CO2 concentration) at a fixed level for the rest of the
photoperiod.  Is this not correct?

John T. Fitch
E-mail: JTFitch at FitchFamily_com
Web Site: www.fitchfamily.com/aquarium.html

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