BBA I've tried everything

[akwarium]

at pH 6.4 the amount of dissolved CO2 is exactly the same as the amount of HCO3, which is your KH.
1 KH is 21.8 mg/l HCO3.

 

[ceg4048]

What is the KH if I might ask?

The KH in the DC should be exactly 4. The KH of the tank water will have no bearing on the KH of the DC.

Cheers,

 

[ceg4048]

at pH 6.4 the amount of dissolved CO2 is exactly the same as the amount of HCO3, which is your KH.
1 KH is 21.8 mg/l HCO3.

This is also not true. Not even close to being true. That's why many people suffer CO2 related faults.

Cheers,

 

[akwarium]

you're right my mistake, forgot about the moles.
HCO3 61 g/mol
CO2 44 g/mol

lets try it again.
at pH 6.4 the amount of dissolved CO2 is exactly the same as the amount of HCO3, which forms the KH, (at least at this pH value)
1 KH is 21.8 mg/l HCO3 is 0.0218 g/l
0.0218/61= 0.000357 mol/l
so for every degree of KH there is 0.000357 mol/l HCO3 and at pH 6.4 that's also 0.000357 mol/l CO2.
0.000357x44= 0.0157 g/l is15.7 mg/l CO2

so at pH 6.4 ( and only 6.4!) 1 KH is 15.7 mg/l CO2 (?)

anyhow, enlighten me why CO2 levels are so crucial for BBA?

 

[FerdinandPorsche]

Yes, if that occurs then it's a good sign, but until you measure the pH change throughout the day it\s very difficult to assess what\s happening. You can have more pearling and still be in trouble.

Cheers,

Again, the pH is still bluish, not complete blue, but bluish. I know this because I have left the water mix to stay for some time and it turned completely blue as opposed to during testing.

 

[ceg4048]

dissolved CO2 is exactly the same as the amount of HCO3

This statement is incorrect. Dissolved CO2 never equals HCO3- unless by some coincidence. Dissolved CO2 is only ever equal to dissolved CO2.

Only a fraction of the gas converts to carbonic acid. Depending on the temperature, somewhere between 1/1000th to 1/600th (0.00001% to 0.000017%) of the gas enters into this carbonic acid / carbonate / bicarbonate equilibrium equation. This is enough to drive a dropchecker, and to change the pH because it changes the ratio of protonated hydrogen (H+) ions to hydroxyl (-OH) ions, which is exactly what the pH of the water indicates.

Also, KH test kits do not measure KH. They measure alkalinity and therefore it is entirely possible to have high KH that is a result of non-bicarbonate products. Those calculations are not valid for real world because we never really know what the carbonate hardness of our water is. We only ever know the alkalinity.

Cheers,

 

[ceg4048]

Again, the pH is still bluish, not complete blue, but bluish. I know this because I have left the water mix to stay for some time and it turned completely blue as opposed to during testing.

If there are no fish in your tank then you really need to turn up the CO2.

Cheers,

 

[akwarium]

This statement is incorrect. Dissolved CO2 never equals HCO3- unless by some coincidence. Dissolved CO2 is only ever equal to dissolved CO2.

Only a fraction of the gas converts to carbonic acid. Depending on the temperature, somewhere between 1/1000th to 1/600th (0.00001% to 0.000017%) of the gas enters into this carbonic acid / carbonate / bicarbonate equilibrium equation. This is enough to drive a dropchecker, and to change the pH because it changes the ratio of protonated hydrogen (H+) ions to hydroxyl (-OH) ions, which is exactly what the pH of the water indicates.

Yes, most CO2 stays CO2. however in most cases there is already bicarbonate in the aquarium water, and there is balance between carbonic acid, CO2, bicarbonate and carbonate depending on pH -value.
Its hard to explain in a language I don't master properly, but maybe this figure shows you what I mean:

Also, KH test kits do not measure KH. They measure alkalinity and therefore it is entirely possible to have high KH that is a result of non-bicarbonate products. Those calculations are not valid for real world because we never really know what the carbonate hardness of our water is. We only ever know the alkalinity.,

Again very true, but the reason why manufactures can get away whit that, is because the difference between alkalinity and KH is usually small. There is no aquarium testing equipment or any calculations that are 100% accurate, but we can make some educated guesses.

remains the question; why is CO2 so crucial for BBA problems?

ps. I hope you are not offended by me being stubborn, I'm just trying to learn...

 

[ceg4048]

Hi,
No, I'm not offended. That's because I know that The Matrix has programmed us to think in a certain way. Your English is fine and I appreciate that you speak it well enough so that I don't have to speak Dutch.

In any case the fact still remains that the chart that you've shown ONLY applies to the 0.00001% to 0.000017% of the CO2 that dissolves in the water.

So whether you calculate the HCO3- added to the water by dissolving CO2 using Molarity or by using simple weight, you must start the calculation by taking the percentage of the dissolved gas that will enter the bicarbonate equilibrium equation FIRST.

So, if for example we take the normal case where you have a cup of distilled (or RO) water (where the KH is zero) sitting on your kitchen counter, we know that generally, the concentration of CO2 that will dissolve from atmosphere into the water will be something like 8ppm. Therefore, only 0.00001% of that 8ppm will enter the HCO3-/Carbonic acid equilibrium equation. The numbers will still be accurate and the pH of the water will fall slightly based on the Carbonic acid generated by atmospheric CO2 dissolving into the water.

In fact this is a problem with pH probe calibration solutions. The liquid is buffered so that it has a particular pH, such as 7.0 or 4.0 but the laboratory knows that air will dissolve in the liquid and the CO2 in that air will slightly acidify the liquid, so they add additional buffer to raise the pH in order to compensate for the acidification. So the calibration solutions are sold as 4.01 or 7.01. Air dissolves in the solution and brings the pH back down to 4.0 or 7.0 and that's what the probe should read.

Furthermore, it is not a valid calculation to simply measure the pH of the tank water and enter that value in the equations because tank water has many organic and inorganic acids already dissolved in the water. This drops the pH of the water and so when you plug that pH value into the equation it will generate a false high CO2 content value. That's the problem pH/CO2 controllers face, because they cannot tell how much of the waters acidity has a component due to the natural acid production of the tank. So, depending on the KH of the tank water the controller will mis-apply the injection rate.

In a dropchecker we use distilled or RO water that is free of any acid or alkaline substances and then that water is adjusted to 4 KH using only a bicarbonate source. That way we know that any change to the pH of the sample can only be due to changes in Carbonic acid from the CO2 injection. Even so, any change in pH of that DC water is caused by the 0.00001% of the dissolved CO2 that enters the DC.

the reason why manufactures can get away whit that, is because the difference between alkalinity and KH is usually small. There is no aquarium testing equipment or any calculations that are 100% accurate, but we can make some educated guesses.

The difference might be small or it might not be. Alkalinity is affected by the content of borate, hydroxide, phosphate, silicate, nitrate, ammonia, as well as the conjugate bases of the tank produced organic acids. Any of these can be present and some are added intentionally in large quantities. I agree that we have to make some guesses and we will be close, but it's more important that we understand that we are guessing.

remains the question; why is CO2 so crucial for BBA problems?

Have a look at the thread Co2 Fluctuations and BBA | UK Aquatic Plant Society

Cheers,

 

[akwarium]

Hi,
No, I'm not offended. That's because I know that The Matrix has programmed us to think in a certain way. Your English is fine and I appreciate that you speak it well enough so that I don't have to speak Dutch.

Thnx,

In any case the fact still remains that the chart that you've shown ONLY applies to the 0.00001% to 0.000017% of the CO2 that dissolves in the water.

the chart is supposed to show how the amounts of carbon acid, CO2, bicarbonate and carbonate relate to each other given a pH value. Not how much of the CO2 will be turned into carbon acid or bicarbonate.

For example:
let say I have a tank whit pure RO water whit a pH of 7 and I start to add CO2. The pH will drop because out of the H2O and CO2, some H+ and HCO3 is formed. More H+ is a lower pH. As long as I increase the amount of CO2 this process will go on and the pH will drop further. But when the amount of CO2 is kept stable, the pH will stabilize: a balance is formed between the amount of CO2 and the amounts of HCO3 (KH) and H+ (pH).

Then I dicide to raise the KH by adding HCO3, some of het HCO3 reacts whit the H+ and forms CO2 and H2O. Less H+ means a higher pH. A new balance is created whit less H+ (higher pH) a little more CO2 and more HCO3. So the pH is higher and there is relatively more HCO3 compared to CO2. Exactly as the figure indicates.

Then I ad a plant that consumes CO2, the balance starts to shift again, the figure indicates that relatively less CO2 means a higher pH (less H+), and that is exactly what happens, H+ reacts whit HCO3....

 

[Jafooli]

Hi Clive,

Thanks for linking Co2 Fluctuations and BBA, while I have hardly any idea what you and awkarium are on about in this thread as its a bit to confusing for me some of it, I found your posts on the other thread very interesting and could understand pretty much all of it along with the other thread you link there discussing about Rubisco and CO2 molecules etc. My only problem is I forget things the next day lol, but just wanted to say how it was a great read.

Which now leads me to my question regarding drop checkers. I've read this thread, the other threads I just mentioned, and even your drop checker tutorial thread.
But have still not found an answer to some of these question.

Does liquid carbon effect the colour of the drop checker at all? I presume not as its not in a gas form, but I would like to understand it a bit better with out getting to scientific. So the CO2 from our diffusers is trying its hardest to escape, and we're trying our hardest to make sure it all dissolves and stay in the water column as long as possible, but how does it work with liquid carbon? does that try to escape the same as our CO2 gas? or as its already dissolved it remains in the water? when we fully dissolve our CO2 gas in the water, is that effectively the same as what liquid carbon is in a bottle? just CO2 molecules?

I'm sure I'm missing something, as everyone would just use liquid carbon instead of pressurised co2 if it was so great , so maybe you have a thread somewhere explaining it? or if not I hope you can just let me know.

Also how are fish going to act when someone is injecting CO2 and Liquid Carbon, it may reach toxic levels? especially if the drop checker cant give you a guide.

I have low light and inject less CO2 over a 200L, around 1.5bps, but yet I cant get my drop checker green. I also see some of my fish may be suffering an hour or two before lights out. So I'm lower it back down a bit later, or I'm see how they act tonight and see if they have adjusted as it was only increased a little few days ago from 1bps. But then again as I use a ceramic diffuser the CO2 concentration may be larger in a certain area of my tank where the gas bubbles rise 30-40ppm, and much less in another area 10-20ppm, so I still need to work on distribution. But it may explain the problem with my fish, if there swimming through the co2 bubbles where its at a higher level, it might be a bit of a shock.

A person with higher KH needs less co2 ? to get in optimum co2 levels, so does a drop checker know this? a person with lower KH may inject more CO2, then much more CO2 gas is going to go into the drop checker to change its PH reading, so I'm a bit confused. I know I need a ph reader to be more precise with co2 levels and stability but I'm sure I read you said a tank with higher KH may need a 0.5 drop in PH where a lower KH tank might need a 1 PH drop. So my drop checker is not going to turn green is it? unless I really increase injection rate and surface agitation.

 

[FerdinandPorsche]

A person with higher KH needs less co2 ?

Hi Jafooli, can I know how true is this statement. I might need to check the dKH in my tank suspecting very low KH.

 

[Jafooli]

Scrap that, I misunderstood. Sorry Ferdinand.

Clive has corrected me below.

 

[ceg4048]

Does liquid carbon effect the colour of the drop checker at all?

Hi Jafooli,
Liquid carbon products have nothing to do with the DC or with the reactions between CO2 and the water. For our purposes, it's better to consider that liquid carbon turns into CO2 by certain reactions only when it is inside the plant, not when it's in the water.

I have low light and inject less CO2 over a 200l, around 1.5bps, but yet I cant get my drop checker green. I also see some of my fish may be suffering an hour or two before lights out.

Yes this is definitely a problem with your flow distribution. If you want to supplement the tank with liquid carbon until you can sort that out it will help, but liquid carbon is expensive. Check our sponsor Aquaessential and they have a much less expensive version of it.

A person with higher KH needs less co2 ? to get in optimum co2 levels

No, this is not true. Why do people believe this? The KH of water has absolutely nothing to do with the solubility of any gas. As I mentioned before in an earlier posts, that is the reason people are confused. CO2 enters the water in exactly the same way in high KH water as in low KH water. Any injection rate being used would dissolve exactly the same amount of CO2 regardless of KH as long as the temperature and pressure of the waters are the same. The difference is that high KH water will neutralize the carbonic acid more easily than in low KH water. That's what alkalinity means. Alkalinity means the ability of water to neutralize acid and to resis the pH change due to acid. So the pH drop when adding CO2 to high KH water will be small due to the alkaline buffers, but the dissolved CO2 is the same. In low KH water, since there is low alkalinity and not much buffering, the pH drop will be greater. Low alkalinity water does not resist changes to pH due to acid addition. So, the same amount of CO2 added to low KH water causes a large shift in pH but only a small shift in pH for the high KH water.

the chart is supposed to show how the amounts of carbon acid, CO2, bicarbonate and carbonate relate to each other given a pH value. Not how much of the CO2 will be turned into carbon acid or bicarbonate.

And that's why you are having difficulty understand this concept. The chart only shows you the relationship of that small portion of the dissolved gas and how that small portion interacts with the water. Because the percentage of the dissolved gas that enters the equation is constant for a given temperature, pressure and salinity, we can then calculate what the total amount of dissolved CO2 is based on the pH drop.

When your DC is lime green and you look at the pH/KH/CO2 table you infer the pH from the color and then you go to the chart. That tells you the dissolved CO2 is 30 ppm in the DC but it does not require all the 30ppm of CO2 to make the DC green. it only requires 0.00001% of 30ppm to turn the DC green. The other 99.99999% is CO2 does NOT turn into Carbonic acid and does NOT turn into HCO3-. You are misinterpreting the chart because what the chart tells you is that the 0.00001% of the CO2 that turns into HCO3- is a representation of (a proxy for) the 99.99999%t of CO2 that is dissolved in the DC water.

That's why CO2 has very little effect on the KH of the water, because the amount of HCO3- formed is a very small amount. The small amount of H+ that results in the equilibrium equation however is enough to change the pH and to therefore change the color of the Bromothymol blue.

Cheers,

 

[ceg4048]

Dropcheckers do not care what the KH of the tank water is. if 30ppm of CO2 is dissolved in the tank water then that 30ppm will evaporate into the airspace of the DC then will dissolve into the DC water and will be 30ppm. That's how a DC works.

Cheers,

 

[Jafooli]

Cheers Clive,

I'm get out of this one before I look even more stupid as I can't even begin to explain what I was thinking, but you've answered my questions now which has helped me to understand the whole scenario much better. I also now know its Alkalinity which plays the key role with the PH drops in different KH tanks, rather than what I was thinking with CO2 and KH.

Hope I've not scrambled your mind FerdinandPorsche

 

[FerdinandPorsche]

Cheers Clive,

I'm get out of this one before I look even more stupid as I can't even begin to explain what I was thinking, but you've answered my questions now which has helped me to understand the whole scenario much better. I also now know its Alkalinity which plays the key role with the PH drops in different KH tanks, rather than what I was thinking with CO2 and KH.

Hope I've not scrambled your mind FerdinandPorsche

I will drop the high kh low co2 theory