C02 & Temperature - The Planted Tank Forum
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post #1 of 6 (permalink) Old 07-16-2005, 09:38 PM Thread Starter
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C02 & Temperature

Started up a cold water planted tank and just wondering if temperature will effect the rate the C02 dissolves. I know that cold water can hold more oxygen then warm but C02 is not co-related to the oxygen content.

After the last 3 weeks it seems that the C02 is dissolving faster (using a bell in the sump) since the bubble size is much smaller then when it was a tropical tank but production from the DIY yeast system is slower because of the colder temps. Currently the measurement is in the "Happy" mark at 15ppm (KH 2, PH 6.6).

Tank temperature ranges between 14 & 18 deg C at the moment. Will be stabilising it at 15C once the chillers up and running.

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post #2 of 6 (permalink) Old 07-16-2005, 10:12 PM
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It does not help to know the answears to your questions,all you have to do is monitor your pH/KH ratio and dont pay much attention to the number of bubbles dissolved because a lot of parameters in the tank can affect the way co2 dissolves.The co2 chart(KH/pH) never lies..
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post #3 of 6 (permalink) Old 07-16-2005, 10:46 PM Thread Starter
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In a way it does matter in my situation . Firstly its just a matter of interest, something I haven't come across browsing C02 related subjects (just plain curious).

It also may effect planned changes to my system. I want to clean up the sump area in the stand. One thing I am thinking of is having a C02 reactor in the chiller cabinet I'm currently making with the outflow dissolving the C02. Since only a small portion of the water will flow through the chiller when on this water will be around the 3deg C mark. The water will flow constantly through the chiller whether it is on or not, thus I could end up with PH swings if C02 is temperature related. I would rather not have to regulate the C02 supply if its not necessary (hard to do with DIY C02)

Just didn't want to go into all the above in the 1st posting.

I could experiment, but if the answer is already out there?

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post #4 of 6 (permalink) Old 07-16-2005, 11:23 PM
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This is an interesting question. The pH-KH-CO2 chart is likely for a constant 25C (78F) temperature. As you said in your first post, non-reactive gases (N2, O2) dissolve better at lower temp. Since CO2 does react with the water to form carbonic acid, I'd assume the effect is less pronounced. However, the lower temp will also change the CO2 equilibria. Without more research (read: when I'm at work with my reference books), I can't really say more with any certainty. At the worst I'd suspect the lower temp will only help, so get to 30ppm CO2 by the chart (pH-kH) and you should be at or above 30ppm at the lower temp.



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2g Mac-quarium. Clown gravel, fluorescent plastic plants, and 2 guppies.
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post #5 of 6 (permalink) Old 07-19-2005, 02:19 PM
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Maybe the link can give you an answer to your question!

The pH-KH-CO2 chart is for a constant 25C (78F), so it do lies at 15C or lower.
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post #6 of 6 (permalink) Old 07-19-2005, 06:49 PM Thread Starter
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Thank you. The chart on that link confirms that the lower the temp the higher the C02 concentration by about 1.5 times between 25C and 5C. Swings will occur if I hitch the reactor to the chiller outlet so will try to come up with another method.

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