# How many bubbles equals one gram of CO2?



## Ags11 (20 Sep 2020)

Just curious, does anyone know how much a CO2 bubble weighs?


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## hypnogogia (20 Sep 2020)

Depends on the size of the bubble. All bubble counters will produce different sized bubbles.  But, I. Sure you could work it out.  How many BBS, hours per day, number of days your cylinder lasts.  If you know the weight of CO2 in the cylinder, then you could work it out.


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## Ags11 (20 Sep 2020)

To answer my own question, the Tropica nano canister has 95 g of CO2 and lasts 600 days at 1 bubble per minute. Assuming they mean it runs 10 hours a day or 600 minutes for 600 days, that’s 360,000 bubbles in 95 grams. Which would be 0.26 mg per bubble.


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## alto (20 Sep 2020)

How do you even run the Tropica Nano System at 1 bubble per minute?
And why assume 10h/day?


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## dcurzon (20 Sep 2020)

there's no solenoid, so presumably its on 24/7, but they use a very low bubble count perhaps in light of it being 24/7
0.109mg per tropica bubble


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## alto (20 Sep 2020)

Tropica Nano System has a needle valve and can easily be switched on/off as needed, you can also install a shutoff valve inline so that you don’t need to disturb needle valve setting 

I do run this 24/7 on my kitchen nano at 1 bubble per 3-4 seconds as that rate is more tricky to adjust with the needle valve (which is really more about the silicon tubing than the valve)


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## zozo (21 Sep 2020)

You could convert it like this also

95 grams of liquid CO² equals 0.052 m³ gaseous volume at 1 bar and 21°C

Thus it always will be approximate if you do not know the temp and atmospheric pressure at the time.
But assume it's the above, then estimate the diameter of the bubble... Then calculate the sphere's volume with
V=4/3 π r 3

Divide  0.052 m³ with V sphere and you should be in the range +/- neglectable bits...


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## Ags11 (21 Sep 2020)

The trouble with that method is getting the size of the bubble right - a small error gets cubed. 

The purpose of this exercise was to compare the delivery rate of the Tropica System 60 to the the Tropica Nano kit. After my cheerful maths and dcurzon's adjustment and assuming 0.11mg bubbles, the System 60 seems to do 3-4 bubbles per minute.


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## zozo (21 Sep 2020)

Any small error is cubed!? An error in reading atmospheric pressure or an error in reading the temperature...

Whatever method you will use there will be small errors... So you never ever will get to the absolutely correct result. 

But even with these small errors using the volume formulas gets you closest of all... Use photography for example to get the bubble size... Use a ruler and a preferably a not round-shaped bubble counter. Place the ruler over the bubble counter and take pictures. Then if you have a picture with a bubble in it then draw 2 straight lines down in the picture from bubble to the ruler. And you'll get a fair idea of the bubble diameter within +/-  0.10 millimetre.

1 m³/1000.000.000 = mm³ 

You know 95 grams =  0.052 m³ gas volume

Once you know the bubble volume in mm³ with  V=4/3 π r 3 

You can calculate the bubble weight into grams... 

The +/- of it all will be awfully tiny...


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## Ags11 (21 Sep 2020)

To lay out the maths, the Tropica recommends filling the reservoir with 80 ml of CO2 for my nano tank. At a density of roughly 1.96 kg/m2, that means the chamber has 150 mg of CO2. With bubbles of 0.11 mg, that’s about 1360 bubbles, or 2.84 bubbles per minute averaged over an 8 hour photoperiod.


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## Ags11 (21 Sep 2020)

@zozo I agree your method is best to weigh a bubble. I guess I changed the objective from “weight of bubbles” to “rate of CO2 injection in mg per minute” with the bubble weight thing only used to express the rate in real world terms.

on the subject of weighing a bubble by measurement, I recall that the surface tension of the sphere raises the pressure inside the bubble. I don’t know by how much though.


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## alto (21 Sep 2020)

Ags11 said:


> The purpose of this exercise was to compare the delivery rate of the Tropica System 60 to the the Tropica Nano kit. After my cheerful maths and dcurzon's adjustment and assuming 0.11mg bubbles, the System 60 seems to do 3-4 bubbles per minute.


Having used both systems, I don’t feel these systems can really be compared in this manner - whatever maths you may’ve used, distribution of the CO2 in the tank is completely different between the System 60 reservoir method and the Nano in-tank diffuser method

The CO2 micro-bubbles can be trapped at the leaf surface and provide localized high CO2 

Diffusion dissolved CO2 into the water column via the reservoir is a very different presentation


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## Ags11 (22 Sep 2020)

Hi @alto - what bubble rate vs tank volume was your nano system set to?


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## Zeus. (22 Sep 2020)

Ags11 said:


> Just curious, does anyone know how much a CO2 bubble weighs?



Its Mass x gravity 🤣 sorry Guys couldn't help that one 

I would say its a pointless exercise as there are so many variables

*CO2 used Database* - may be helpful in some small way


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## alto (22 Sep 2020)

Ags11 said:


> Hi @alto - what bubble rate vs tank volume was your nano system set to?


30cm cube, moderate substrate, hardscape, Eheim MiniUp filter, ONF Flat One Nano + (love this light!)

1bubble per 2-3s will grow Eriocaulon cinereum https://tropica.com/en/plants/plantdetails/Eriocauloncinereum(091TC)/19547
When I let the tank transition to non-CO2, the E cinereum slowly disappeared (over months)

1 bubble per 3-4s supported a mix of various plant (Tropica med to advanced)
When I let the tank (again) go non-CO2, plant growth slowed ... and it’s a crazy jungle in there so difficult to suggest which plants have suffered from mainly lack of CO2 vs mainly lack of light

(Note this tank has also had few water changes and no water column fertilizers, tap is very soft, pH 6ish - livestock is a few snails)

Meant to add this photo for @dw1305


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## dcurzon (23 Sep 2020)

dcurzon said:


> there's no solenoid, so presumably its on 24/7, but they use a very low bubble count perhaps in light of it being 24/7
> 0.109mg per tropica bubble



so if a bubble is roughly 0.11mg, then there are
1g = 1000mg
1000mg/0.11mg = 9090.90... bubbles per gram.

Not all bubbles are made equal, so I guess we could round that down to 9000 bubbles per gram.

a 2kg FE would provide
2000(grams of co2 in FE) x9000 (bubbles per gram) = 18000000 bubbles per 2kg FE.

At 2bps for 8 hours a day...
2x60 = 120 (bubbles per minute)
120x60= 7200 (bubbles per hour)
7200x8 = 57600 (bubbles per 8 hours)

18000000\57600 = 312.5

so expect 312 days from a 2kg FE at 2bps for 8 hours/day. Or roughly 10.5 months


Ive no idea if that works out according to peoples experience!


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## dcurzon (23 Sep 2020)

Lol, I did a google, and the first hit says that a Dennerle co2 bubble weighs an average of 0.125mg
https://www.aquaristikshop.com/aquaristic/Dennerle-CO2-Bubble-Counter-Exact/902059/

using the 0.125mg as a base, our 2kg FE at 2bps would last 277 days.  Which is 35 days less.

Today, I connected a new 2kg FE, and set my bps to 2.5bps.  This should last 222 days, so I should need to replace it on 3rd May 2021... lets see how that works out!


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## Ags11 (23 Sep 2020)

Interesting we got to 0.11 mg from back of envelope calculations of the Tropica Nano CO2 and Denerle bubbles are pretty close by at 0.125 mg.


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## dcurzon (24 Sep 2020)

I guess a more accurate method would be to put the canister on scales, take the weight premco2 on, and take the weight post co2 off, then divide by the number of bubbles in that period.  It'll give an average per bubble for YOUR bubbles, then you can work the rest out from that.  Probably best to do it over several days for more accuracy.

If I owned scales I'd give that a go myself.


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## Sergey (24 Sep 2020)

Did anyone talk about the pressure on the output end? Say you use a diffusor that requires certain pressure to let the gas through, so the pressure on the output end will be higher -> the pressure of gas inside a bubble will be higher -> the mass of the bubble will be higher at the same bubble volume. 
That's if my physics don't fail me


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## Ags11 (24 Sep 2020)

The pressure of the bubble will be water pressure + additional pressure from the surface tension of the bubble. The output pressure should only affect bubble rate not bubble pressure.


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## dcurzon (12 May 2021)

dcurzon said:


> Lol, I did a google, and the first hit says that a Dennerle co2 bubble weighs an average of 0.125mg
> DENNERLE CO2 Bubble Counter Exact
> 
> using the 0.125mg as a base, our 2kg FE at 2bps would last 277 days.  Which is 35 days less.
> ...


I'm a week past this forecast and on the same bottle.
Edit: I was starting to doubt myself, however I changed from in-tank to in-line diffuser at some point so I would have adjusted BPS


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