Measuring disolved CO2? - The Planted Tank Forum
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post #1 of 6 (permalink) Old 03-14-2007, 02:54 AM Thread Starter
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Measuring disolved CO2?

Hi all. So I got my regulator, bubble counter, diffusor and tubing today. (Thanks Aquabuys!!)

I assembled everything and it's working fine. I have read about measuring total CO2 using the ph and kh chart but I don't have a kh test kit. Well, I acually do but a loaned it to someone and they lost the reference card.

Right now I have it set for 2-3 bubbles per minute in a 46 gallon moderate/heavily planted tank with medium/moderate fish load. My ph is 7.6

I thought I read somewhere where you can measure ph then let the water sit for 24 hours and test it again to determine CO2. Is this a reliable method? Where can I find those instructions? Thanks.
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post #2 of 6 (permalink) Old 03-14-2007, 03:16 AM
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Take a bit of your tank water and place in a shallow container. Let this sit for one to two days and stir it a couple times during the wait period. Now test it for ph. Shoot for 1 point or more below that value when your co2 is running. Is it reliable? I think its better than relying on kh values to determine ph.
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post #3 of 6 (permalink) Old 03-14-2007, 03:47 AM
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A better method would be to use a drop checker w/ a standardized kH solution.
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post #4 of 6 (permalink) Old 03-14-2007, 12:17 PM
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Originally Posted by epicfish View Post
A better method would be to use a drop checker w/ a standardized kH solution.
Maybe so, but aren't these still subjective to color interpretation? I mean....."green is good", "blue is too little" seems a little wishy-washy to me. But I guess that's all you are getting with PH test kits too.
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post #5 of 6 (permalink) Old 03-14-2007, 06:31 PM
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I would think that you still need to know what your originating KH is to find out what CO2 levels are when you get a PH reading. Just buy another KH test kit. With the Aquarium Parmacuiticals brand the KH is determined by the number of drops it takes for the color to change from blue to yellow. What brand are you using?
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post #6 of 6 (permalink) Old 03-14-2007, 08:47 PM
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IMHO, i think the best thing to do is to do BOTH methods. It's definitely a good idea to have an idea of where your KH and pH are, and since certain things can throw off the pH/KH/CO2 table, it's good to double-check your results with the other method. The other method isn't super exact - it just gives you a general idea of how much CO2 is dissolved - but that's all we're looking for.
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