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[APD] Re: CO2 off at night

Same thing in my tank. What I believe to be the cause is surface agitation,
I used to run my CO2 24/7 but I needed to make sure there was some surface
agitation from the canister output to avoid overdosing at night. Today I do
the opposite, I have a powerhead driven reactor on a timer and hardly any
surface agitation at all. My PH tends to drop by 0.2 over the night period
when the reactor is turned off. I decided to turn the reactor off at night
to allow me to inject more CO2 during the day without risking PH crashes at
night. I was having problems keeping up with the rate of CO2 uptake towards
the end of the day cycle so this seemed to solve it for me. My CO2 in the
morning is now 30ppm (PH6.6) and 18-19ppm (PH6.8) at the end of the day
cycle. BTW this is a 4wpg tank.

Giancarlo Podio

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  b.. Subject: Fw: [APD] Re: CO2 off at night
  c.. From: "John T. Fitch" <JTFitch at fitchfamily_com>
  d.. Date: Fri, 12 Sep 2003 10:29:43 -0400
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Sorry, but this is not what happens in my tank.  At night, when there is
no CO2 added to my tank, the pH does *not* go "up as CO2 diffuses out of
the tank."  The pH goes down from 6.9 (my controller set point) to 6.7 or
6.6.  How would this be possible if the *net* flow of CO2 is out of the

In the morning, when the lights come on, the pH level slowly rises over an
hour or two back up to 6.9.  At that point, the contoller turns the CO2 on
and off for the rest of the day. This keeps the pH from rising any
further, and hence the CO2 concentration from dropping any further, during
the photoperiod.

Earlier, I tried to explain what I thought was happening.  Now I am only
reporting what actually happens.

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

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