Dissolving CO2 & O2 - The Planted Tank Forum
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post #1 of 3 (permalink) Old 05-04-2015, 03:41 AM Thread Starter
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Dissolving CO2 & O2


I diffuse CO2 through my canister filter using it as a giant reactor. The CO2 goes in the intake from a glass diffuser and it comes out from the outflow pipe. I have placed the output pipe just one inch below the surface so it can generate some 'mild' surface agitation. Is this an efficient way to dissolve CO2 into the tank? I'm asking you this because the outlet both pumps CO2 in the water and generates surface movement. Does a lot of the CO2 gas out this way? Should I place the filter output lower?

Thanks in advance,

By the way, the PH doesn't change much from the beginning of the day until the CO2 shuts off at night. It only goes from 7.2 to 7.0.
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post #2 of 3 (permalink) Old 05-04-2015, 05:09 AM
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If the pH is only changing by 0.2 from adding CO2 to the water, the amount of CO2 in the water after adding the CO2 is about 3ppm times 10 to the 0.2 power, or about 5 ppm. That is very low, but is helpful for a low light tank. That should tell you that you are either not using a high enough bubble rate of CO2, or the CO2 you are adding is outgassing from the water agitation.

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post #3 of 3 (permalink) Old 05-04-2015, 05:57 AM
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CO2 enters my 75 gal much the same way, except I use a reactor plumbed into the canister outflow. The outflow pipe is positioned a couple inches below the surface (no spray bar) and it creates a fairly strong surface agitation.

The PH drops about 1.15 from completely degassed tank water. Obviously surface agitation is going to out gas some, I just keep it cranked to make up for whatever loss there happens to be.

To get a more accurate measure of how much the PH drops, sit a bowl full of tank water out for 24-36 hours, and test the PH of that. Measuring against current tank water at the beginning of the day assumes 100% of CO2 from the day before has out gassed. That is not always the case. So you may have a higher concentration that you think.

But it sounds like you probably need to add more co2.

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