RE: [APD] CO2 use - off at night? -- or - plugging timers

["Giancarlo Podio" <gp at isaconsulting_com>]

In theory that works, but it's assuming that the plants are the only
"consumers" of CO2. In my experience thats not the case, gas exchange has
proven to be the biggest consumer of CO2 in my tanks to date, and that
obviously doesn't slow down at night. Unless you have a very low rate of gas
exchange in your tank, which could possibly indicate insufficient water
flow, you will likely find that most of the CO2 is simply being lost to the
atmosphere and that the plants only account for a very small percentage of
the total CO2 lost/used during the 24 hour period. I too started off with
solenoids and powered reactors connected to my light times.... but in the
end I found that the most stable conditions were simply running CO2
non-stop. I have since sold or given away my solenoids. Obviously your tank
may differ, but it's worth trying it to see for yourself, just set your
alarm so you can check PH during the night hours and you'll likely find that
it's just as stable if not more stable than turning the CO2 off.

Obviously those who keep a very low KH may indeed need a PH controller and
solenoid to avoid large swings from small changes in CO2 levels, changes
that not only occur during the night but also following regular prunings,
water changes and other interventions in the tank. But if your KH is 3-4 or
above you shouldn't have any problems IMO.

Giancarlo Podio

----- Original Message ----- 

  a.. To: "'aquatic plants digest'" <aquatic-plants at actwin_com>
  b.. Subject: RE: [APD] CO2 use - off at night? -- or - plugging timers
  c.. From: Sean Kettle <kettles at videotron_ca>
  d.. Date: Thu, 10 Jun 2004 18:43:30 -0400
  e..

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----

Well, since the CO2 isn't being used at night, it's reasonable to assume the
system shouldn't have to inject a great deal (if any) to maintain the pH.
My guess would be that at lights off, there would be minimal injection of
CO2 in the first place.

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