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Re: oxygen deficiency/co2

>Date: Sun, 06 Jul 1997 09:27:15 -0500
>From: Daniel Hawley <dhawley at iamerica_net>
>I continue to have major problems with my 100 gallon Dupla set up. I have
>had to aeriate the past couple of nights to stop my fish from gasping for
>air in the morning
> ...
>and a Dupla co2 delta sytem using a Dupla
>reactor 400 controlled by a Neptune AquaController. 
> ...
>My KH is 7, GH 3, PH 6.8-7.5, fe
>0.2 mg/l and the NO2 level is 0.1 mg/l all measured using Dupla test kits.
> ...
>The tank is very heavily
>planted with good plant growth, had to harvest twice in the past month. 

>I have several questions the first is how do I get enough oxygen in the tank
>to get us through the night. 

If everything is working properly, this should not be a concern.  However,
everything is NOT working properly. 

>I also would like to know how to determine the
>co2 set point, is it the PH reading just before the lights come on? 

If your measurements are correct, your CO2 level is varying between 33 mg/l
(pH=6.8) and 8 mg/l (pH=7.5), i.e., from way too high to too low. I assume
the Neptune controller is supposed to control the CO2?  It's NOT doing this. 

If I were you, I would have a pH of 7.0 to 7.1 as a goal.  With your KH,
that will give you 17-22 mg/l of CO2. The controller should have its set
point at 7.05 (if it has that fine a resolution).  Most controllers will
turn the CO2 on when the measured pH is 0.05 above the set point and turn
it off when the pH is 0.05 below the set point.  A variance of 0.1 is the
"hysteresis" of the controller -- it isn't designed to hold the pH at a
single point. 

You don't seem to have your controller set up correctly.  Check the

>I have been considering replacing the Eheim 217 with a Eheim wet/dry model
>2229, is this a good idea? 

I don't see any reason to do this.  Once your controller is workign
properly, you should not have a problem with oxygen.

George Booth, Ft. Collins, Colorado (booth at frii_com)
Need info? http://www.frii.com/~booth/AquaticConcepts.htm