CO2 by air..?

[Mitchel]

Another noob question.

Hypothetically: there's a lots of CO2 in the air, about 400 ppm.
When you dose this air into a tank by, an air pump and a diffuser, then you automatically get higher CO2 values, right?
So why we add CO2 in gaseous form. Is that more concentrated or something? 🤔

 

[LMuhlen]

400ppm translates to 0.04%.
The CO2 we inject is probably very close to 100%.
Or you can see it as CO2 from injection being close to 1,000,000ppm

It is hugely different.

Due to the equilibrium laws for the dilution of gas into water, from what I read, those 400ppm balances at ~3ppm CO2 in water

 

[Jaseon]

Theres a few good experiments on CO2 v no CO2 on youtube that show the differences.

Im guessing non CO2 tanks can vastly be improved by having more agitation at the surface to increase that gaseous exchange. That might be a worthwhile experiment on its own with non CO2 tanks.

 

[dw1305]

Hi all,

400ppm translates to 0.04%.
The CO2 we inject is probably very close to 100%.
Or you can see it as CO2 from injection being close to 1,000,000ppm

That is the one, CO2 is a very minor component of the atmosphere, but <"incredibly soluble">.

Due to the equilibrium laws for the dilution of gas into water, from what I read, those 400ppm balances at ~3ppm CO2 in water

There has been a lot of discussion as to where the 3 ppm figure comes from, because <"theoretically it is only about 0.6 ppm">.

cheers Darrel

 

[tiger15]

If you aerate your water with an airstone, there is good chance you strip more CO2 out of water than injecting more in. Your fish and bacteria respire and generate CO2 above the atmospheric equilibrium level off photo period without agitation.

 

[jaypeecee]

There has been a lot of discussion as to where the 3 ppm figure comes from, because <"theoretically it is only about 0.6 ppm">.

Hi @dw1305

Perhaps the 3 ppm figure comes from that wonderful aquatics source from many years ago. I'm referring to The Krib. Please take a look at the following:

CO2 ``FAQ''

In the text, there is a statement that "With a typical equilibrium dissolved CO2 level of 2-3 ppm, this gives us a "natural" pH of around 7.7".

JPC

 

[Mitchel]

so much for my theory 😆
Txs you'll for the answers

 

[dw1305]

Hi all,

Hi @dw1305

Perhaps the 3 ppm figure comes from that wonderful aquatics source from many years ago. I'm referring to The Krib. Please take a look at the following:

CO2 ``FAQ''

Yes, that's it, it is the George and Karla Booth reference linked in the earlier post, by @xim

Cheers Darrel

 

[tiger15]

Years ago I calculated aqueous CO2 concentration based on Henry coefficient and 400ppm atmospheric CO2 and came up with less than 1 ppm. The calculation is complicated by unit conversion as unit weight of air is much lighter than water, and Henry coefficient is temperature dependent. Also indoor CO2 is typically higher than outdoor, and can be time and house dependent. I don’t trust the calculation and find it more credible to just leave a bucket of water overnight and measure aqueous CO2 by kH and pH that turned out to be roughly 3 ppm within measurement errors.

I recently bought a CO2 meter to monitor my house indoor air. It’s winter time and all windows are closed and the measured ambient CO2 fluctuated from 400 ppm in the morning to 480 in the evening at cooking time. My house has gas heat and stove, and a house with electric utility, different number of occupants and seasons is expected to behave differently. In a crowded room or small tight room, ambient CO2 have been reported to exceed 1000 ppm

 

[PARAGUAY]

so much for my theory 😆
Txs you'll for the answers

It's good to ask these questions .UKAPS as ever explains

 

[dw1305]

Hi all,

Years ago I calculated aqueous CO2 concentration based on Henry coefficient and 400ppm atmospheric CO2 and came up with less than 1 ppm. The calculation is complicated by unit conversion as unit weight of air is much lighter than water, and Henry coefficient is temperature dependent. Also indoor CO2 is typically higher than outdoor, and can be time and house dependent. I don’t trust the calculation and find it more credible to just leave a bucket of water overnight and measure aqueous CO2 by kH and pH that turned out to be roughly 3 ppm within measurement errors.

We have a thread that may be of interest: <"Determination of CO2 in combination with an aquasoil">.

....... This one <"Dissolved CO2 in freshwater systems">, has some figures, that suggest that lakes and rivers typically have between four and eight times more CO2 than they would at equilibrium (0.6 ppm CO2), so we are back somewhere near the "3ppm CO2" figure. The other issue in vegetated water would be that you would get big diel variations in CO2 & O2 levels (back to <"Canford Park again">).....

I recently bought a CO2 meter to monitor my house indoor air. It’s winter time and all windows are closed and the measured ambient CO2 fluctuated from 400 ppm in the morning to 480 in the evening at cooking time. My house has gas heat and stove, and a house with electric utility, different number of occupants and seasons is expected to behave differently. In a crowded room or small tight room, ambient CO2 have been reported to exceed 1000 ppm

We <"have them in the lab.">, if you get to 2000 ppm CO2 they sound an alarm and turn the gas and electric off.

cheers Darrel

 

[LMuhlen]

Someone mentioned in some other thread that if we kept 5000ppm CO2 concentration in the air, we could go for massive surface agitation and balance at 30ppm dissolved CO2. I have this idea in the back of my head to make a semi-sealed tank, with a CO2 meter controlling the atmosphere. From times to times, a small fan would renew the atmosphere partially. Then I could do away with the oxygenation vs CO2 dilemma for surface agitation. I could agitate all I want and have both.

 

[tiger15]

Hi all,

We have a thread that may be of interest: <"Determination of CO2 in combination with an aquasoil">.


We <"have them in the lab.">, if you get to 2000 ppm CO2 they sound an alarm and turn the gas and electric off.

cheers Darrel

O2 demand and CO2 release in soil is significant component of climate model, but was missed out in the Biodome experiments in Arizona leading to unsustainable O2 level unsafe for experimenters. I think 3000 ppm is the upper limit of CO2 for safe operation of green houses.

 

[dw1305]

Hi all,

Someone mentioned in some other thread that if we kept 5000ppm CO2 concentration in the air, we could go for massive surface agitation and balance at 30ppm dissolved CO2

True, but I'm not sure it is a workable idea.

I'll be honest, for me I'm not too worried about submerged CO2 levels. I always have floating (and sometimes emergent) plants and <"they have access to ~420 ppm CO2">.

<"Dissolved oxygen does interest me">, and I'm always willing to trade CO2 loss for <"higher dissolved oxygen levels">.

cheers Darrel

 

[Aqua sobriquet]

I know I’ve only got a few easy to grow plant types in my two Nano’s but I don’t have any CO2 and the plants grow like mad. Substrate is just sand as well.

 

[Myrtle]

I recently bought a CO2 meter to monitor my house indoor air. It’s winter time and all windows are closed and the measured ambient CO2 fluctuated from 400 ppm in the morning to 480 in the evening at cooking time. My house has gas heat and stove, and a house with electric utility, different number of occupants and seasons is expected to behave differently. In a crowded room or small tight room, ambient CO2 have been reported to exceed 1000 ppm

We have these at the school I work in; the government helpfully gave enough for every classroom in every school to alert us to ventilate the room to reduce the spread of covid. It's amazing how fast the CO2 builds up in a room full of kids.

 

[tiger15]

CO2 builds up quickly inside the car to 1000+ ppm if you don’t turn on venting. Outdoor CO2 fluctuates between 385 to 425 seasonally due to photosynthesis and furnace operation.

 

[dw1305]

Hi all,
We got the CO2 monitor up to 2000 ppm by breathing into, I think the highest it has been otherwise is about 1200 ppm with bunsen burners on.

Outdoor CO2 fluctuates between 385 to 425 seasonally due to photosynthesis and furnace operation.

The lowest level is <"higher than that now">. This is today's graph.

cheers Darrel