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Some silly questions about CO2 bubbles

Colombo: Just one more thing.
If Jose, T.Barr or anyone else is saying that CO2 mist is better for plant growth, how do you measure it's concentration? How can you be sure that 30 ppm CO2 in fully dissolved form is the same as 30 ppm CO2 in gas form?
If I paraphrase it, you say that if we have two tanks with the same conditions (same volume, same substrate, same plants, same nutrients level ... with only difference being CO2 form), and in the first one we have CO2 mist (in gas form) while in the second one we have fully dissolved CO2 (in aquatic form), then the plants will grow faster/better in the first tank. My question is, how do you measure the mist CO2 concentration? Do you have any special mist CO2 meter for it? Or how do you know that you have the same concentration of CO2 in both tanks? The only CO2 we are able to measure is the one in fully dissolved (= gas) form. If CO2 is not dissolved yet, we are not able to measure it. Do you get my point? So if it would be true that CO2 mist is better for plants then it would mean that they get much more higher CO2 concentration than is the concentration of fully dissolved CO2 in water. And if this is true, then you don't have same conditions in both tanks, so your comparisson is not valid.
Maybe CO2 mist is more effective way of CO2 supply (you supply smaller amount of CO2 gas into your tank to get high CO2 concentration), but if you ensure the same high CO2 concentration in fully dissolved form, the plants may grow just as fast. So again, if you want to compare the plant growth rate using CO2 mist vs. fully dissolved CO2, then you have to ensure the same concentration of both forms in your tank. But there is no way to measure the CO2 mist concentration as all CO2 meters are able to measure just the fully dissolved CO2.

Lets see Ardjuna, to see the difference between the two forms you only need to inject exactly the same ammount of co2 into the tank. One time dissolve it all and the next time use an atomizer of some sort. The BPS are kept the same so whatever difference you see should be due to the different co2 forms in water because the total co2 injected is the same. So you dont need fancy co2 measuring kits here only a bubble counter. You dont measure the dissolved co2 because as you say this is not measuring the bubbles. This is clearly explained in the link I added.

There are more questions to be answered like:
1) How do plants grow with only co2 bubbles and the least dissolved co2 possible like in ADA tanks?
2) Has the size of the bubbles got any effect?
3) Probably co2 bubbles have less an impact at higher co2 ppm

Toms Barrs experiments show mostly a middle ground where you dissolve quite a lot of co2 but still have micro bubbles.

I like these kinds of conversations even if they look crazy to hobbyists because I think this is where you learn the most.
 
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To see the difference between the two forms you only need to inject exactly the same ammount of co2 into the tank ... whatever difference you see should be due to the different co2 forms in water because the total co2 injected is the same. So you dont need fancy co2 measuring kits.
The problem I see here is that you are comparing the same amounts of CO2, not the same concentrations of CO2. I understand what you want to say, and I agree that if you add, for example, 5 grams of CO2 into your tank in the form of bubbles vs. in the form of fully dissolved gas there may be some differences in growth rates. I also agree that we can show the difference (if there is any) by a simple growth experiment with two identical tanks which will differ just by the CO2 form (CO2 mist vs. fully dissolved CO2). This will show us what CO2 form is better for plants.

But as to the concentration of CO2, this experiment won't help. Because if your question was "Do plants grow better under 30 ppm CO2 in the form of bubbles or under 30 ppm CO2 in the fully dissolved form?", then you have no relevant way to measure the concentration of CO2 bubbles. And this was my point. Whenever you measure CO2 concentration in your tank, you measure solely the dissolved CO2. The CO2 in the form of bubbles which are not yet dissolved do not add to this ppm concentration. So if you measure 30 ppm CO2 in your tank where you use a CO2 atomiser (CO2 mist), then this measurement tells you that you have 30 ppm CO2 in dissolved form + unknown amount of CO2 in the "bubble form". And because of this unknown variable you won't be able to compare it ... in a proper, objective way.

So you say (and maybe you are right, maybe not) that CO2 bubbles pose some advantage over fully dissolved CO2 for plants, but you can hardly compare these two in terms of concentrations. Do you see what I mean?

There are more questions to be answered like:
1) How do plants grow with only co2 bubbles and the least dissolved co2 possible like in ADA tanks?
2) Has the size of the bubbles got any effect?
3) Probably co2 bubbles have less an impact at higher co2 ppm
ad 1) Whenever there is a CO2 bubble in water, from the very moment it gets out of the diffuser it begins to dissolve in water. So there is nothing like CO2 bubbles without any dissolution. In ADA tanks the dropcheckers are green which means that at least about 30 ppm CO2 dissolved in water. The rest may escape to air, but still 30 ppm CO2 is in the water in the dissolved state.
ad 2) The size of the bubbles has effect on the time the bubble can remain in the water. The bigger the bubble the harder to keep it in the water. Smaller bubbles have more time available to dissolve.
ad 3) This can be as well due to the concentration issue. As the concentration of dissolved CO2 comes close to the concentration of "bubble CO2", the difference is no more as prominent (noticeable). We know that in the bubble the CO2 concentration is ~100% (or a little less due to its impurities). In the water the concentration is much more less. But when the concentration of CO2 in the water reaches the "saturation point" (which may be somewhere around the 40 ppm CO2), the difference plays no role anymore.
 
So you say (and maybe you are right, maybe not) that CO2 bubbles pose some advantage over fully dissolved CO2 for plants, but you can hardly compare these two in terms of concentrations. Do you see what I mean?

I see what you mean but it doesnt make sense to me. How can you measure efficiency of two ways of co2 diffusion if total co2 going in is different because you need to get the same dissolved ppm? I think maybe what you want to know is what works better, if 30 ppm (dissolved) with mist or 30 ppm (dissolved) w/o mist am I right? Well if the theory discussed is right then 30 ppm (dissolved) with mist will work better (Think about it). Why? Because if with same co2 ammount injected mist works better then for the mist method we will need more co2 to get the same ppm (dissolved) yet the effect will still be better. You would be adding more co2 with the mist method as to get more dissolved co2.

Basically you cannot measure concentration because this depends on the diffusion method and you actually want to know which method is best in growing plants. Concentration is not independent here, total co2 used is. You have to choose a variable that stays constant for both methods.

ad 1) Whenever there is a CO2 bubble in water, from the very moment it gets out of the diffuser it begin to dissolve in water. So there is nothing like CO2 bubbles without any dissolution. In ADA tanks the dropcheckers are green which means that at least about 30 ppm CO2 dissolved in water. The rest may escape to air, but still 30 ppm CO2 is in the water in the dissolved state.

Yes, this is why I said minimum dissolved co2, because there is always going to be some dissolved. I think ADA is the least efficient mist method in dissolving co2. ADA levels are not high at all and I bet they keep climbing through the day (look at surface movement). so they might be 30 ppm (dissolved) at the end of photoperiod and maybe 5 at the start. ADA in Japan never uses a dropchecker, but ADA in Poland etc do. Dropcheckers here dont say nothing because they will measure all co2 in the water weather dissolved or in bubbles.

ad 2) The size of the bubbles has effect on the time the bubble can remain in the water. The bigger the bubble the harder to keep it in the water. Smaller bubbles have more time available to dissolve.
Yes, but I mean subtle changes in the size of the bubbles whilst keeping them small enough to travel around the tank. Subtle changes in size might have an impact and there might be an "ideal size". There is no proof for this and its just a question I ask myself.

ad 3) This can be as well due to the concentration issue. As the concentration of dissolved CO2 comes close to the concentration of "bubble CO2", the difference is no more as prominent (noticeable). We know that in the bubble the CO2 concentration is ~100% (or a little less due to its impurities). In the water the concentration is much more less. But when the concentration of CO2 in the water reaches the "saturation point" (which may be somewhere around the 40 ppm CO2), the difference plays no role anymore.
You dont know this. Concentration in a CO2 bubble is approx 1964ppm. You cant reach this conc in water so you cant know the effect of bubbles at different co2 ppms (dissolved) if you dont do the experiments. The role the bubbles play might be less each time as conc goes up but you cannot say they wont play a role. Even if the role is not important it doesnt matter because we are more interested in the role it plays from 0 to 30 ppms (dissolved) because the idea is to have less dissolved co2 in our tanks as to make it safer for fish etc.
It looks like if anything is non limitting it might be the conc in a co2 bubble. Maybe Im wrong and it turns out 80 ppm of co2 is the same as the mist method. But the mist method would still be safer and simpler.
 
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"Do plants grow better under 30 ppm CO2 in the form of bubbles or under 30 ppm CO2 in the fully dissolved form?"
If you are comparing ppm then they have to be mg of co2/1 Kg of water. This is not the case of a bubble so what you want to compare is not comparable. Totally different things.

ppm of the water=mg of co2/1 Litre of water
ppm for a bubbles= mg of CO2/1 Litre of CO2

There is no such thing as 30 ppm of co2 in the form of bubbles.
 
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Have you noticed how Tom advises to position a spray bar - vertically rather than horizontally. Hmmm...

I noticed that too Andy. I've not seen any tanks on here with that configuration but as this was 10 years ago, maybe horizontal has been proved to be better?

Hope Jose and Ardjuna don't mind me interrupting.:)
 
I noticed that too Andy. I've not seen any tanks on here with that configuration but as this was 10 years ago, maybe horizontal has been proved to be better?

Hope Jose and Ardjuna don't mind me interrupting.:)

Has anyone seen Tom Barr use a spray bar in any of his tanks? Really, spray bar vs nozzle, which one is better is just a preference, not a fact.
 
Has anyone seen Tom Barr use a spray bar in any of his tanks? Really, spray bar vs nozzle, which one is better is just a preference, not a fact.

Nobody was talking about nozzle v spray bar. It was the orientation of the spray bar that was mentioned by Tom.
 
Mine is vertical ,
the spray bar is in the top right corner vertically, with the flow pointing towards the middle of the tank , the filter part of the pump has a plastic shroud which I have drilled a hole to insert my co2 pipe , i m running a diy kit using yeast, and the bubbles being produced are tiny, the pump is horizontal in the tank so the co2 entering it sits with the water flowing through it before it builds up enough to be sucked through and blown out the spray bar

Im quite surprised how fast the plants are growing , every day I can seethe amount of growth :)
 
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