re: DIY CO2 Injection

From: "Jan Fidrmuc" <J.Fidrmuc at kub_nl>
>I have already leart that DIY CO2 injection can be made from 2L soda 
>bottles and that the mix should be 2 cups of sugar, 1 tsp of baking 
>soda and 1 tsp of yeast. I understand the bottle should be filled 
>almost to the top with watter then. 

The measurements you indicated are the ones I use, so I'll add an extra
comment.  I do not attempt to control the cottony bacterial buildup that can
occur in yeast CO2 systems.  I understand that filling the bottle to nearly the
top can encourage this growth.

>Besides the composition of the mix, 
>does the temperature matter much? I have some of my tanks in 
>a rather cold room - the tanks have heater though. 

From what I remember of chemistry, 10 degrees Celsius is roughly equal to
doubling any given reaction rate, so yes, temperature will have an effect on
the rate of production.

>And, is it possible 
>to kill the fish by injecting too much CO2 - either by making the 
>carbon dioxide replace oxygen in watter of by making the Ph drop too 
>much? If so, how can I controll how much CO2 is injected with this 

It is possible to kill your fish by injecting too much CO2.  CO2 does not
replace dissolved O2 in water, it can just reach lethal doses in extreme
circumstances.  If I remember correctly, 30 ppm is approaching lethal doses in
at least some fish.  15 ppm is the usual desired amount for a brightly lit
plant tank, and atmospheric balance is around 2 ppm if I remember correctly.
You can measure your CO2 levels by measuring your KH and your pH and consulting
the table at the bottom of the CO2 FAQ, located at:


>Finally, I understand the CO2 will make the Ph drop. Should I 
>counter this by adding some baking soda to the tank watter?

My goal is KH=5 and pH=7.0.  My tap water makes the KH portion easy, but I
don't always inject enough CO2 most of the time to get the pH down to 7.0.
This combination works out to 15 ppm CO2 in the water.  With my yeast system, I
adjust the efficiency of my CO2-water reactor mechanism to try and balance out
the pH at 7.0.

I hope this helps,

David W. Webb
Enterprise Computing Provisioning
Texas Instruments Inc. Dallas, TX USA
(214) 575-3443 (voice)  MSGID:       DAWB
(214) 575-4853 (fax)    Internet:    dwebb at ti_com
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