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That definitely is not similar. Using atmospheric air, you can only achieve <0.5ppm of CO2 in water.
BC
I discovered by accident that if air is forced into a turbo diffuser, it can achieve similar result (plants bubbling) as using CO2. But what I am not sure is that if the bubbling of the plants is due to saturation of other gasses contained in the air (e.g. O2) or CO2.
Anybody has explored the topic before?
Thanks
That definitely is not similar. Using atmospheric air, you can only achieve <0.5ppm of CO2 in water.
BC
How long was it running on air? It will be interesting if the result is consistent for a week.
I have always wanted to know what the CO2 concentration is like in a typical stream or pond where plants thrived. Where CO2 is dependent only on water/air gas exchange. Could it be higher than ambient 0.5ppm?
Which brings me to think aloud whether if a none CO2 tank with 2.5~3wpg light is sustainable by Seachem Excel alone.
sounds plausible... the turbo diffuser would then be "forcing CO@ to diffuse into the local ised H20 medium. But then there's this question: If this works, then surely using highly efficient airstones/venturi valves might experience this same effect, if to a lesser value? Yup, maybe u could try to do some tablution over the week, n maybe do some CO2 testing? imagine if this were true! LFS CO2 biz would be dealt a death blow!!
Do keep us updated please!
knowledge is alway better shared than hoarded
YC
Based on the % of CO2 in the atmosphere, and the equilibrium constants, partial pressure, etc. ... it is not possible to have any higher concentration of CO2 in water by bubbling atmospheric air into water, no matter what method used.
Just pure equilibrium calculations... not considering CO2 additions via microbial activities, respirations, chemical & biological decomposition etc. In natural water bodies, CO2 could be up to 5ppm or higher (if I don't remember wrong) due to such activities, not by CO2 from atmosphere. Although there are such activities in our aquarium, it will never bring the CO2 level up to that supplied by bubbling CO2 into the water.
BC
Thanks for the overwhelming replies.
bclee: I am interested in the physic/chemical principles you explained. If I were to increase the flowrate of air into my turbo reactor, wouldn't it dissolve more CO2 into the water? Could you elaborate on it please.
Geoffrey: I did not tested it for a week as it was due to suction of air from surface skimmer. A day after I observed the bubbling, the canister filter started to make noise. I had to stop it for fear that it might damage the filter.
But there is only a very small percentage of CO2 in the air. Most of it, N2 and O2 - Composition of Air. To bring it up to the level we need is quite impossible using that method.
The three major components of atmospheric air are:
N2 (Nitrogen) ~ 78%
O2 (Oxygen) ~ 21%
CO2 ~ 0.3%
These gases have different solubilities in water depending on the air pressures. If I am not mistaken, CO2 is the most soluble of the three gases under normal atmospheric pressure. N2 becomes highly soluble only high pressures such as deep water diving, that's why for deep sea diving, N2 has to be substituted with an inert gas, namely helium.
When CO2 dissolves in water, it becomes carbonic acid, thereby lowering the pH of the water. Unfortunately carbonic acid is rather unstable and breaks down into CO2 and water when agitated (eg, fizzling of carbonated soft drinks; note such drinks are bottled at pressures of about 14 atmospheres to force the CO2 to dissolve into the solution).
Therefore, forcing atmospheric air into a stone diffuser and bubbling at the bottom of the tank, both these acts increases the pressure and therefore the solubility of the CO2. However, at the same time, the agitation caused by too much aeration will result in the breakdown of the dissolved CO2. Thus, trying to balance the dissolved CO2 using pumped atmospheric air is a delicate balance of pressures and minimal agitation.
[quote:0ac4f58f0e="gks"]
Therefore, forcing atmospheric air into a stone diffuser and bubbling at the bottom of the tank, both these acts increases the pressure and therefore the solubility of the CO2. However, at the same time, the agitation caused by too much aeration will result in the breakdown of the dissolved CO2. Thus, trying to balance the dissolved CO2 using pumped atmospheric air is a delicate balance of pressures and minimal agitation.[/quote:0ac4f58f0e]
v informative. Query: Dosent a reactor cause alot of agitation in the water too? Wouldnt that be working against the dissolution of CO2?
And for the case od a turbo diffuser, maybe it causes high enough pressure w/o too much agitation, ths causing more CO2 than ordinarily possible to dissolve? Just wondering...
knowledge is alway better shared than hoarded
YC
[quote:840bf3b7dc="gks"]
...However, at the same time, the agitation caused by too much aeration will result in the breakdown of the dissolved CO2. Thus, trying to balance the dissolved CO2 using pumped atmospheric air is a delicate balance of pressures and minimal agitation.[/quote:840bf3b7dc]
"breakdown of the dissolved CO2"...How can that happen??? No way...
What agitation does is to drive the system to reach the static equilibrium state faster. Now we got to define the "system"...
Let us take the equilibrium to be between the atmosphere and water... the static equilibrium CO2 concentration is <0.5ppm. If the water has CO2 > 0.5ppm (normal CO2-enriched aquarium will contain 20-30ppm CO2), agitation at the interface between water/atmosphere will drive the concentration down towards <0.5ppm, ie CO2 escape into the atmosphere.
If we take the CO2 reactor... the equilibrium is between the CO2 bubble and water. The CO2 bubble is CO2 rich, in contrast with atmospheric air. The static equilibrium between CO2-rich bubble and water is probably a few hundred ppm or higher. Therefore, agitation will cause the CO2 to dissolve into the water from the CO2 bubble.
If I have the time, I will try to post the CO2 calculations here.
BC
[/b]
[quote:dd870fec71="gks"]
....
When CO2 dissolves in water, it becomes carbonic acid, thereby lowering the pH of the water. Unfortunately carbonic acid is rather unstable and breaks down into CO2 and water when agitated (eg, fizzling of carbonated soft drinks; note such drinks are bottled at pressures of about 14 atmospheres to force the CO2 to dissolve into the solution).
Therefore, forcing atmospheric air into a stone diffuser and bubbling at the bottom of the tank, both these acts increases the pressure and therefore the solubility of the CO2. ...[/quote:dd870fec71]
In making of carbonated water, one pressurises with almost pure CO2 (not atmospheric air).
To achieve 20ppm of CO2 by pressurising atmospheric air, you will need > 40atm of pressure which is not achievable by merely forcing air through stone diffuser.
BC[/b]
Hmm... now I understand what it is about. Thanks bclee. Well explained.Let us take the equilibrium to be between the atmosphere and water... the static equilibrium CO2 concentration is <0.5ppm. If the water has CO2 > 0.5ppm (normal CO2-enriched aquarium will contain 20-30ppm CO2), agitation at the interface between water/atmosphere will drive the concentration down towards <0.5ppm, ie CO2 escape into the atmosphere.
If we take the CO2 reactor... the equilibrium is between the CO2 bubble and water. The CO2 bubble is CO2 rich, in contrast with atmospheric air. The static equilibrium between CO2-rich bubble and water is probably a few hundred ppm or higher. Therefore, agitation will cause the CO2 to dissolve into the water from the CO2 bubble.
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