CO2 vs H2CO3 vs HCO3-

basically , the way I understand it, the CO2 is taken in as CO2 the carbon is basically scrubbed off during the photosynthesis process. leaving O2 behind.


at least in trees it works that way.

aquatic plants may not be that much different.

carbonic acid rings a bell (H2CO3). At least that is what I understand as the cause for the lowering of pH.

I have only read the first part of this article but it may help shed some light on what happens when you inject CO2 into an aquarium

http://en.wikipedia.org/wiki/Carbonic_acid

This article touches on it briefly but I thought it was very interesting.

http://www.thekrib.com/Plants/phisio.html

yes ,that is a direct cause of the co2 reacting in the water..more of s byproduct of adding the CO2.

the plants breath and still use CO2..we know they do.
O2 is a direct result of the carbon being scrubbed off the CO2 and off gassed by the plant.(photosynthesis).the reverse happens when the lights go out..the plants will use O2.organisms tend to use things when found in the simplest forms. the plants have a mechanism that allows the to use CO2 much like the way humans use O2.

What you're talking about is the Carbonic Anhydrase reaction.
C02 + H2O -->H2CO3--> HCO3- + H+
For it to happen, you need the enzyme Carbonic Anhydrase. It's very important for plasma buffering in animal blood and I've only studied it in animal physiology so I can't tell you if plants or bacteria have it. If they do, you can expect the reaction to be occuring in the tank.

1.CO2 is added to water, it's still CO2.
If you add baking soda, it's still HCO3 and Na.

2. CO2, then a few might use HCO3 if there is no CO2 available, there are two methods for that, direct uptake and indirect uptake.

3. Search aquatic macrophytes, HCO3 (bicarbonate) and uptake.
Bowes has done the most research on the topic. Use Google scholar.

H2CO3, is a weak acid, it is very weakly disassociated. So you have very little H2CO3 relative to CO2, we just assume it's all CO2. If you want a precise amount, at least for seawater, it's about 400 CO2's for every 1 H2CO3 for a ratio of dissociation.

Some people think they can change the KH/HCO3 using CO2, that's rubbish and they need to get that monkey business out of their heads asap.

If you want more CO2 in the water, ..........well.........add more CO2, it's so obvious folks miss the simple solution.

That's what plants want, not a KH/HCO3 really.

Regards,
Tom Barr