Beginner: will aeration add more CO2?

10963 Views 3 Replies 4 Participants Last post by Hilde, Dec 17, 2010

takadi

Discussion Starter · Dec 13, 2010

I just started about three months ago. I originally got plants as a source of oxygen (started out with anacharis), but my collection slowly built up to the point where now it is a decent jungle. I have mostly frills, horworts, and swords, with four leaf clover, microsword, chainsword, moneywort, and cabomba scattered around. My 75 g tank is moderately to heavily stocked with both fish and plants and I have about 196 w of light for 6 hours and 96w of light for 10 hours. Before I think about Co2 injection, I want to see if there are still some low tech options out there, as I am trying to keep my budget at a minimum. I am currently dosing with Flourish excel, but I have a feeling that it isn't enough, especially since I've recently bought some dwarf baby tears. Did some KH-PH-CO2 calculations and according to that, my Co2 hovers around 2-8 ppm.

I am getting differing opinions. Some people say that aeration would increase Co2 absorption into the water through equilibrium. Others say that though Co2 will be absorbed faster into the water through aeration, it will also out-gas even faster actually resulting in lower net Co2 in the water. Either way, with my situation, would I be able to get away with any low tech option or is Co2 injection a must? I still wanna know out of curiosity sake if aeration actually makes Co2 concentration better or worse

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random_alias

· #2 · Dec 13, 2010

http://www.hallman.org/plant/booth2.html

linked web page said:
After letting the water equilibrate for one day we measured dissolved CO2 at 2-3 ppm. We then set up a large powerhead to circulate the water (Project RS-500, ~500 gph) and let it run for a day. The CO2 remained about 2-3 ppm. At the end of most of the tests, CO2 again measured about 2-3 ppm, indicating that this was the equilibrium value for the experimental conditions (note that the altitude was 5000 feet above sea level).

If you are not adding CO2 to the aquarium water, then letting it sit or aerating it will still leave you with roughly the same atmospheric equilibrium, approximately 3 ppm.

takadi said:
Some people say that aeration would increase Co2 absorption into the water through equilibrium. Others say that though Co2 will be absorbed faster into the water through aeration, it will also out-gas even faster actually resulting in lower net Co2 in the water.

Assuming no appreciable CO2 introduction or production in your aquarium, if you have two substances that reach an equilibrium with each other, increasing or decreasing their surface area will not cause one to loose any more or the other to gain any more, since they have already reached a state of equilibrium. When water has 3 ppm and the air has 3 ppm, there is an equal concentration and so no "pressure" difference. There is no movement across the barrier that is not met with equal and opposite movement. Think of it like this, you put one man on each side of a rope and they pull evenly against each other. There is no movement. Now, add 100 more men to each side of the rope, all of them also pulling equally. There is still no movement. A stalemate is a stalemate.

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Diana

· #3 · Dec 16, 2010

However, if you have a lot of plants removing the carbon dioxide faster than it is replaced (fish, decomposing matter, gas exchange with the air), then increasing the surface movement might raise the CO2 level in the water. Not higher than that equilibrium, though.

If your tests showed that the water was lower in CO2 than the air, then it would help.

Use a drop checker, not a GH/pH/CO2 chart. While there are ways of figuring out how to use those charts most accurately, a drop checker can be read quickly and often, so you can get an idea of how CO2 levels change through the day.

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Hilde

· #4 · Dec 17, 2010

Here are some tanks without Co2.

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