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Old 01-29-2007, 03:53 PM   #1
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How much CO2 is enough?

I've got a tank that is low light and lightly planted.
20 gallons
30 watts at 5000K (wich gives off a sort of yellowish color sort of unpleasant)
Four plants -Amazon sword fern, dwarf anubus, and two bulb plants I can't identify (they have large bulbs and long flowing grass like growth about a cm wide long runners under the substrate).
Flourite substrate
I've put a flourish nutrient tab under the Amazon Sword as I don't think they are really a low light plant (as the LFS guy told me).

I would like to expand the growth with other low light plants and I wonder... do I need CO2 injection?

I like the idea but I don't think I can live with two 2-liter bottles near the tank. I wonder, can I get by with 750ml glass container (like a wine bottle)?

It will give off less CO2 so I wonder is a little CO2 better than none?

How do I measure CO2?

I've read of the effects of CO2 on water hardness (or is it the reverse?) but I haven't seen KH test kits beside the ammonia and Nitrate test kits. Is there clear explanation of this relationship somewhere? I've read the sticky here about making a reference solution but there is some foundation information I am missing in order to understand it.

Well that has got to be close to the limit on number of questions per post.

Thanks for any help

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Old 01-29-2007, 04:01 PM   #2
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Little or fluctuating CO2 is worse than no CO2. It will lead to algae problems you dont want. Since it only 20 gallons maybe give Excel a try. The answer to your question is yes, CO2 will help plants grow better even under low light, but it needs to consistent which you would not get from one 750 ml reactor.

Co2 does not effect water hardness it does cause the PH to drop.

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Old 01-29-2007, 05:14 PM   #3
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Thanks, I will try the Excel.

But out of curiousity, does it take 4 liters of the sugar, yeast, water recipie to create a stable amount of CO2 pressure or can it be done with one two liter bottle? What is the formula here?

Is it x psi over a period of time requires y pounds of sugar?
If the period of time varys then don't the other factors vary?

This must be written down somewere but I can't seem to find it or wrap my head around it.


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Old 01-29-2007, 08:27 PM   #4
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There are many variables that affect how much volume you need to generate CO2 for a tank. The type of yeast used. The mix used. The temperature. The method of diffusion. How much of the CO2 is being gased off by various factors. How densely planted the tank is.

A good starting place is to set up 2 Liters of CO2 generation for every 10 gallons of tank. Perform some testing to see how effective it is and tweak from there.

Also DIY CO2 will never create a truly "stable" amount of CO2 in tank. It's variable by nature. There are some steps that can be taken to help alleviate the natural variability of the CO2 mix, but they never completely eliminate it. These include rotating when the mixes are changed so that one is always going strong while another is petering out or just starting up and changing out the mixes before they are completely spent.
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