# Potassium Carbonate (K2CO3) vs pH ?



## MichaelJ (12 Jan 2022)

Hello, anyone of you chemistry wizards know the guiding math for how much a certain amount of K2CO3 will raise the pH?

2.5 grams of K2CO3 dissolved in 100 liter of water will raise the KH by 1 degree and add ~14 ppm of K and ~11 ppm of CO3 - but since K2CO3 is a relatively strong base how much will it affect pH? 

Haven't been able to find any good guiding references relative to pH.

Cheers,
Michael


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## JoshP12 (13 Jan 2022)

Hey @MichaelJ!

Could use pH/KH chart and just look when the CO2 is around 3 for the new pH (based on your new projected KH).

Example:





If your KH was zero, and you added enough to go to .5, then your pH would probably be around 6.6/6.7 and it was probably at something like 6.2/6.3? before. If you remember < this post > that guy used pure RO and had low KH around 0 --- pH around 5.7 ... probably some of that "extra" from 6.2ish would have been just decay, acids, or even error in test kit (below 6 is harder to see with bromothymol, unless he has a probe - even then calibrating is not fun).

Suppose you were at 1.5, added enough for a 1 degree increase, call it 2.5 now -- pH around 7.4. Call it a bit lower since we never quite hit the 3ppm in tank, then mask it slightly based on age + decomposition ... 7.2?

Hope that helps.

The actual shift in carbonate equilibrium can be calculated - would have to sit down and do it- but I think the above approximation works.

Josh


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## MichaelJ (13 Jan 2022)

Hi @JoshP12  Thanks much appreciated. I am still trying to figure this one out..

I did some rudimentary testing earlier today. I made two buckets of 10 liter of RO water @ TDS 7. Amounts below measured out on a fairly accurate microgram scale and tested using the fairly inaccurate API pH and KH test kits. However the TDS checks out almost spot on using my Hanna TDS meter vs the amounts of Potassium and Carbon trioxide in the K2CO3 that I added.

Bucket 1: To increase the KH by 1 I added 0.25 gram of K2CO3 and measure a pH at about 7 (could be anything between 6.5 and 7.5) and measure TDS at 32

Bucket 2: To increase the KH by 2 I added 0.50 gram of K2CO3 and measure a pH at about 9 (maxes out the Wide pH API test) and measure TDS at 54 (should be 57).

I can draw a line between these two points, but I am sure there is a more rigid mathematical correlation here. ?  Even though I studied up quite a bit on basic chemistry lately, I realize I am still just mostly a math and computer science guy 

Cheers,
Michael


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## hypnogogia (13 Jan 2022)

Ph scale isn’t linear, it’s logarithmic.


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## JoshP12 (13 Jan 2022)

MichaelJ said:


> Hi @JoshP12  Thanks much appreciated. I am still trying to figure this one out..
> 
> I did some rudimentary testing earlier today. I made two buckets of 10 liter of RO water @ TDS 7. Amounts below measured out on a fairly accurate microgram scale and tested using the fairly inaccurate API pH and KH test kits. However the TDS checks out almost spot on using my Hanna TDS meter vs the amounts of Potassium and Carbon trioxide in the K2CO3 that I added.
> 
> ...



There are maths - this might give a lens into it:


			https://lawr.ucdavis.edu/classes/ssc102/Section5.pdf
		


You will need to fix co2 with a bubbler or something in the bucket.

Also, I cross referenced Rotala butterfly and it gave me 492 mg - might sound silly but 8mg in 10 L will make a difference if you compound that error throughout.


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## X3NiTH (13 Jan 2022)

The Potassium Ion is a strong base so in the first instance there is enough acid neutralisation of the water to balance out at a lower pH adding more pushes the equilibrium further, the pH addition from the carbonate has its own rise but the potassium is busy forming hydroxides which have a much greater effect on pH hence the sky high reading.


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## Ria95 (13 Jan 2022)

given the complex chemistry of the aquarium water the easiest way is to test on a small sample, but as you found out the initial pH will increase a lot. It will decrease over time as the CO3 gets converted to HCO3 by CO2 (atmospheric or injected). This is the reason most prefer to prepare their water a few days before  and aerate heavily. Alternatively you can use KHCO3.


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## Ria95 (13 Jan 2022)

A Brønsted-Lowry base is a proton acceptor. The potassium ion is a cation (fewer electrons than protons, positive charge), so it will not want to accept more protons but rather donate them, so not a base. K+ is not considered to have much in the way of acidity or basicity  One can easily test how little K affects the pH by adding KCl at an equivalent K concentration. Then adding Na2CO3, MgCO3 or CaCO3 at an equivalent CO3 cocentration and see the major increase.


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## MichaelJ (13 Jan 2022)

Ria95 said:


> given the complex chemistry of the aquarium water the easiest way is to test on a small sample, but as you found out the initial pH will increase a lot. It will decrease over time as the CO3 gets converted to HCO3 by CO2 (atmospheric or injected). This is the reason most prefer to prepare their water a few days before  and aerate heavily. Alternatively you can use KHCO3.


Hi @Ria95 Yes, seems like Potassium bicarbonate (KHCO3) might be a better choice if I can avoid the huge and "unpredictable" spike in pH - I just need to raise the KH in my RO water to about 1.5 and at the same time provide a fair amount of potassium.

Cheers,
Michael


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## arcturus (13 Jan 2022)

MichaelJ said:


> Hi @Ria95 Yes, seems like Potassium bicarbonate (KHCO3) might be a better choice if I can avoid the huge and "unpredictable" spike in pH - I just need to raise the KH in my RO water to about 1.5 and at the same time provide a fair amount of potassium.


The issue with using KHCO3 to remineralize the RO is that we cannot keep the remineralizer mix and the fertilization mix independent due to K. Using KHCO3 to raise 1.5 dGH adds ~20 ppm K in the process. 

The fertilizer mix uses monopotassium phosphate (KH2PO4) for PO4, which will further increase K. This means we probably need to find another source for NO3 because KNO3 will further increase K. Magnesium nitrate Mg(NO3)2 might be an option. 

But this raises a question about the fertilization regime. With this mix, we would be adding almost 100% of the weekly K at water change. But NO3 and PO4 would then be added incrementally during the week... or should they also be added at the same time as K, during the WC?  Has anyone experience dosing at near EI levels (with CO2 injection) just once a week, at WC?


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## X3NiTH (13 Jan 2022)

KCl is charge balanced in water whereas K2CO3 isn’t so hydroxide has to form to balance the charge.


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## dw1305 (13 Jan 2022)

Hi all,


Ria95 said:


> One can easily test how little K affects the pH by adding KCl at an equivalent K concentration.





X3NiTH said:


> KCl is charge balanced in water whereas K2CO3 isn’t so hydroxide has to form to balance the charge.


I was just going to write that, anyway now I'll agree.





@X3NiTH  is right, potassium chloride (KCl) is a <"neutral salt"> because is the product of the reaction between a strong base (KOH) and a strong acid (HCl).  Potassium (K) is a <"group one alkali metal">. Group 1 metals are highly reactive and only occur as compounds (salts), <"those salts are all soluble">.

If you had any meaningful amount of K2CO3 the pH will rise, if you wanted to work out theoretically how much you would need, <"the calculations are here">.   

cheers Darrel


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## MichaelJ (13 Jan 2022)

dw1305 said:


> If you had any meaningful amount of K2CO3 the pH will rise, if you wanted to work out theoretically how much you would need, <"the calculations are here">.


Thanks Darrel, thats exactly what I was looking for  

Cheers,
Michael


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## MichaelJ (13 Jan 2022)

arcturus said:


> The issue with using KHCO3 to remineralize the RO is that we cannot keep the remineralizer mix and the fertilization mix independent due to K. Using KHCO3 to raise 1.5 dGH adds ~20 ppm K in the process.


That is fine with me... I was intending to use the K2CO3 if I can get it to work, or the KHCO3 as a replacement for the Tap water I am mixing in with my RO water... (My tap water runs thought a KCl resin based water softener so I have a huge amount of K and plenty of CO3 in my tap water but no Ca or Mg so I essentially source all my CO3 and Potassium from my tap water, but I also get unknown quantities of other compounds...) The idea was to lower my TDS a bit by not adding as much K (and potentially Cl)  But looking at the numbers for KHCO3 I am starting to think this is going to be a wash vs. my overall TDS as KHCO3 will add an additional 17ppm to my TDS compared to K2CO3 for the KH 1.5 and K (20 ppm).  Then I might as well just stick to what I am doing now with my Tap water mix.



arcturus said:


> The fertilizer mix uses monopotassium phosphate (KH2PO4) for PO4, which will further increase K.


Yes, but only fairly marginally - if I target 5 ppm of PO4 I only get 2 ppm of K...



arcturus said:


> This means we probably need to find another source for NO3 because KNO3 will further increase K. Magnesium nitrate Mg(NO3)2 might be an option.


Yes, I am using Mg(NO3)2 which I think works well.



arcturus said:


> But this raises a question about the fertilization regime. With this mix, we would be adding almost 100% of the weekly K at water change. But NO3 and PO4 would then be added incrementally during the week... or should they also be added at the same time as K, during the WC?  Has anyone experience dosing at near EI levels (with CO2 injection) just once a week, at WC?


I am not injecting CO2 but I do my whole dose of EI level dosing once a week. I usually mix it into my WC water.

Cheers,
Michael


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## Wookii (13 Jan 2022)

The real question we have to ask @MichaelJ is why we are bothering to add carbonates and increase the KH at all (and I’m including myself in that ‘we’ because I add K2CO3 to remineralise my RO also).

I have always added it as something of a safety net to counter the assumed pH reducing effects of CO2 injection. However I’m acutely aware I’m doing this blindly without any real understanding of why. @dw1305 or @X3NiTH might be able to explain why it isn’t really necessary.

For practical examples, @Conort2 (if you read his journal here) injects CO2 whilst maintaining a zero KH with no ill effects.

Edit: sorry, I’ve just read you don’t inject CO2 anyway, so the case for not adding anything to boost the KH is even stronger.


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## MichaelJ (13 Jan 2022)

Wookii said:


> The real question we have to ask @MichaelJ is why we are bothering to add carbonates and increase the KH at all (and I’m including myself in that ‘we’ because I add K2CO3 to remineralise my RO also).



Your absolutely right @Wookii,  My answer would be that I want that little bit of buffering that 1-2 KH would give in terms of stabilizing my pH... But I am definitely not 100% sure if I really, really need it.  If I would think enough about it, I would ask myself why would my pH not be stable ? what could possibly cause "severe" pH swings in a healthy well-maintained low-tech tank, and would said swings even be an issue for my plants or livestock?



Wookii said:


> I have always added it as something of a safety net to counter the assumed pH reducing effects of CO2 injection. However I’m acutely aware I’m doing this blindly without any real understanding of why. @dw1305 or @X3NiTH might be able to explain why it isn’t really necessary.
> 
> For practical examples, @Conort2 (if you read his journal here) injects CO2 whilst maintaining a zero KH with no ill effects.
> 
> Edit: sorry, I’ve just read you don’t inject CO2 anyway, so the case for not adding anything to boost the KH is even stronger.



Yes, your probably right... but still, I am not 100% sure zero KH is the way to go....  But I would love to hear what the experts have to say on the matter.

Cheers,
Michael


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## Ria95 (13 Jan 2022)

It really depends on the lifestock and the bioload of the tank. A little KH can go a long way if you don't have a lot of acid producing reactions in the tank. Other components like phosphates can buffer the pH and prevent wild swings. 




X3NiTH said:


> The Potassium Ion is a strong base


Please see in the image posted by Darrel which component of K2CO3 goes on to act as a proton acceptor and is labeled a base. That is the point I am making. 


dw1305 said:


> View attachment 179890


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## dw1305 (14 Jan 2022)

Hi all,


Ria95 said:


> which component of K2CO3 goes on to act as a proton acceptor and is labeled a base





Ria95 said:


> A Brønsted-Lowry base is a proton acceptor


I like the <"Bronsted-Lowry"> definition of acids and bases, I think it <"makes things easier">. I'm not a chemist and I really struggled with alkalinity and buffering before it was explained to me in terms I could understand.


dw1305 said:


> ....... OK, this is because KH2PO4 is an acid (you have two hydrogen atoms), and the tests for dKH actually measure alkalinity. You've added an acid ("H+ ion donor"), so alkalinity has declined.
> 
> The conjugate base for KH2PO4 is K2HPO4 (which is a base or "H+ ion acceptor", because you have two potassium atoms) and together they are phosphate buffers which you can combine together, in differing proportions, to make <"buffered solutions of a known pH">.
> 
> Carbonate hardness (dKH) is also a measure of a buffered system, but in this case the acid and base are CO3-- (HCO3-) and H2CO3 (from CO2). If you want to add carbonate hardness you can use potassium bicarbonate (KHCO3) (or potassium carbonate (K2CO3)), have a look at <"Questions regarding....">, there are amounts to add at <"James' Planted Tank">


<"Potassium (K) is basic">. If you look at the periodic table of the oxides of elements, bases are to the left and the acids to the right (excluding the "noble gases"). 







> Periodic table showing basic (blue), amphoteric (green) and acidic (red) oxides. The metal-nonmetal boundary is indicated by the grey staircase line.





> Water is an amphoteric compounds. A substance that can act either as an acid and as a base.
> 
> H2O molecules may either donate a hydrogen ion or accept one. This property makes water an amphoteric solvent. In the situation where an acid dissociates in solution, water is acting as a base. Conversely, water acts as an acid when bases dissociate. ..........



cheers Darrel


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## Wookii (14 Jan 2022)

MichaelJ said:


> ... But I am definitely not 100% sure if I really, really need it.
> 
> Yes, your probably right... but still, I am not 100% sure zero KH is the way to go....



I'm not sure either to be honest, it would be good to get a definitive answer. Obviously in natural bodies of water like blackwater habitats you frequently get very low TDS, and presumably zero carbonates - but I am cautious in comparing a natural body of water with a glass box.



Ria95 said:


> Other components like phosphates can buffer the pH and prevent wild swings.



Do you know what levels phosphates would need to be in the water column in order to successfully achieve that. For example would the typical dosing ranges of 1-3ppm be sufficient?




dw1305 said:


> Hi all,
> 
> 
> I like the <"Bronsted-Lowry"> definition of acids and bases, I think it <"makes things easier">. I'm not a chemist and I really struggled with alkalinity and buffering before it was explained to me in terms I could understand.
> ...



The chemistry is well above my paygrade Darrel.

In terms of the query in laymans terms, if using RO water do we need to be adding carbonates? I know you use rainwater, but I've not seen you mention adding any carbonates salts directly?

If we don't any carbonates what are the risks if any, and how does that picture change if we inject CO2?


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## Ria95 (14 Jan 2022)

Nice find on the table. Please notice that the table describes K2O as a basic oxide , not "the potassium ion" K+ . There is a difference. In a similar manner one can say KOH is a base, NaOH is a base, -OH is a base.  K+ ,  Na+ is  not a base . A Brønsted-Lowry base is a proton acceptor. If we have a proton  H+ is it more likely to be accepted by OH-, CO3 (2-) or by K+ ? It's really that simple in this case. 

It may be worth highlighting that when we add KHCO3 or K2CO3 to our aquariums at no point are we adding metallic potassium (K). We are adding the potassium ion K+.  Here is a video showing how K metal looks and reacts with water  . 



Wookii said:


> Do you know what levels phosphates would need to be in the water column in order to successfully achieve that. For example would the typical dosing ranges of 1-3ppm be sufficient?


It will buffer at any concentration. If it's enough to prevent swings depends on how much acid is produced, other buffers in the system... At 3ppm it's a small player compared to 1KH from HCO3


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## dw1305 (14 Jan 2022)

Hi all,


Wookii said:


> In terms of the query in laymans terms, if using RO water do we need to be adding carbonates? I know you use rainwater, but I've not seen you mention adding any carbonates salts directly?


Assuming I wasn't keeping black water fish I would probably add 1 or 2 dKH, for the reasons @MichaelJ alludes to.  Because our rainwater has some carbonate buffering I never actually start from 0 dKH, in the way I would if I used DI water.

I've never tried DI water and 0 dKH, so I don't have any practical experience of it. I work with what I've got (rain-water) and try and find plants and fish that do well in it. If I had softer rain water, and I didn't have a hard tap supply, I would probably keep more obligate soft water organisms, and if I was obliged to use our tap water? I'd keep "hard water" fish and plants.

The other reason for having some dKH is that I like <"snails in the tank">, so I need some carbonate buffering for them. Now I just watch the red Ramshorn Snail shells and if all the <"snail shells are really pale">, and all the snails are small, I add a <"dash of tap water">,  which is <"about 17dKH / 17 dGH">. 

cheers Darrel


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## dw1305 (14 Jan 2022)

Hi all,


Ria95 said:


> Please notice that the table describes K2O as a basic oxide , not "the potassium ion" K+ .


I maybe missing something, but isn't that why the table uses the oxides? The oxygen doesn't change, but the oxides are either basic, amphoteric or acidic. Group one and group two oxides are basic, because these are <"alkali"> and <"alkaline earth"> metals respectively, but the point is that they are the *alkaline metals*.

As an example of an acidic oxide, one that people will be familiar with <"because it is how a drop checker works">, carbon dioxide (CO2) (in solution) lowers pH and this is because a small proportion of the gas becomes carbonic acid (H2CO3) and that then disassociates into H+ and HCO3- ions.

A proton is H+, we've added a proton and "proton donors" are defined as acids. If we want to know how much acid we've added? We can use a <"modified titrimetric method with a base of known strength and a narrow range pH indicator">.


Ria95 said:


> It may be worth highlighting that when we add KHCO3 or K2CO3 to our aquariums at no point are we adding metallic potassium (K). We are adding the potassium ion K+. Here is a video showing how K metal looks and reacts with water


Yes, agreed, you are never going to find potassium (K) as a metal, it is much too reactive. It oxidises in air and water, so you have to store in oil to keep it as potassium metal.

In nature potassium is always going to be in a mineral or solid compound or as an ion (K+), in solution (or bound to a clay, etc) and plants can only take up mineral nutrients as ions from solution.

cheers Darrel


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## Soilwork (14 Jan 2022)

Hi All,

Just a warning about inverts when using potassium bicarbonate.  All my shrimp acted very strange and erratic after using it to raise pH.  All MTS closed up in their shells and all crypts melted.  May have added way to much to my soft water.  Potential ammonia issues becoming toxic as pH rose that was never confirmed but it unlikely.  I suspect the sudden TDS change was the issue given the melting of the crypts.  I repeated this to confirm it was after adding potassium bicarbonate so not a fluke.  Only other thread I could find was the one below.  Never used it since.  









						Potassium (bi)carbonate and inverts
					

I wanted to start a conversation on this because I haven't seen too much mentioned and I wanted to see if anyone else has had a similar experience to mine.  I switched to RODI water several months ago. I used a potassium bicarbonate product to raise my KH to ~3, yielding approximately 40 ppm K...




					www.plantedtank.net
				




Regards 

CJ


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## MichaelJ (14 Jan 2022)

Soilwork said:


> Hi All,
> 
> Just a warning about inverts when using potassium bicarbonate.  All my shrimp acted very strange and erratic after using it to raise pH.  All MTS closed up in their shells and all crypts melted.  May have added way to much to my soft water.  Potential ammonia issues becoming toxic as pH rose that was never confirmed but it unlikely.  I suspect the sudden TDS change was the issue given the melting of the crypts.  I repeated this to confirm it was after adding potassium bicarbonate so not a fluke.  Only other thread I could find was the one below.  Never used it since.
> 
> ...


Hi @Soilwork  Thanks. It essentially brings it back to my OP,  because when I realized that potassium carbonates is a relatively strong base I wanted to understand the possible implication on pH without just having to wing it by measuring it with my pH test kit and possibly take comfort in a crude / erroneous low reading. With very soft water (in CO3 terms), It is very likely that an abrupt change to pH freaked out your shrimps - and regardless of KH, a large abrupt change to TDS definitely will - and might also have affected the crypts.  It's the pH bit that worries me though. I keep my TDS change fairly consistent and never introduce more than a 10% net change with my 40% WCs.

Cheers,
Michael


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## MichaelJ (14 Jan 2022)

Ok, as a test I tried targeting ~1.3 KH with 330 mg of K2CO3 in 10 liters of RO water. That gave me a pH around 7.5, which is reasonably consistent with the math @dw1305 pointed to above, so for tomorrows WC's I think I will just target that and should give me 18 ppm of K as well   ... this should work out.

EDIT: Just to test: In the 10 liter test bucket above I added another 170 mg. to reach 2 KH... and it immediately spiked to pH ~9... Note to self: dosing K2CO3 is definitely not something you want to do with a cavalier attitude!

Cheers,
Michael


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## dw1305 (15 Jan 2022)

Hi all,


MichaelJ said:


> Just to test: In the 10 liter test bucket above I added another 170 mg. to reach 2 KH... and it immediately spiked to pH ~9... Note to self: dosing K2CO3 is definitely not something you want to do with a cavalier attitude!


If you have calcium (Ca++) (or magnesium (Mg++)) ions in solution they will always moderate the pH to ~pH8. This isn't dependent on how much potassium carbonate (K2CO3) you add (until you run out of divalent cations).

This happens because of the <"common ion effect"> and the <"limited solubility of calcium and magnesium carbonate">.

cheers Darrel


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## Nick potts (15 Jan 2022)

Soilwork said:


> Hi All,
> 
> Just a warning about inverts when using potassium bicarbonate.  All my shrimp acted very strange and erratic after using it to raise pH.  All MTS closed up in their shells and all crypts melted.  May have added way to much to my soft water.  Potential ammonia issues becoming toxic as pH rose that was never confirmed but it unlikely.  I suspect the sudden TDS change was the issue given the melting of the crypts.  I repeated this to confirm it was after adding potassium bicarbonate so not a fluke.  Only other thread I could find was the one below.  Never used it since.
> 
> ...



I use KHCO3 to raise my KH to 1 in my RO water, I have only been using it a few weeks but have so far not noticed any issues with my shrimp colonies. Is this an issue only if using large amounts?

I also haven't checked the PH of my freshly made water, but the tank runs at 7.3 before CO2 injection and 6.2 after.


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## MichaelJ (15 Jan 2022)

dw1305 said:


> Hi all,
> 
> If you have calcium (Ca++) (or magnesium (Mg++)) ions in solution they will always moderate the pH to ~pH8. This isn't dependent on how much potassium carbonate (K2CO3) you add (until you run out of divalent cations).


So what your saying is, if I would start out adding my typical target of CaSO4.2H2O (~30ppm) and then add the K2CO3 I wouldn't see the spike, as the Ca would moderate/stabilize the pH around the equilibrium?  If so, that makes me less worried about the situation.

Cheers,
Michael


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## dw1305 (15 Jan 2022)

Hi all, 


MichaelJ said:


> I wouldn't see the spike, as the Ca would moderate/stabilize the pH around the equilibrium?


Yes.

cheers Darrel


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## MichaelJ (15 Jan 2022)

dw1305 said:


> Hi all,
> 
> Yes.
> 
> cheers Darrel


Awesome Darrel, thanks for clarifying... yeah, I suspected my experiment was a bit construed given that I was using pure RO water. I will run an experiment where I start adding all my minerals and salts (MgSO4,CaSO4,Mg(NO3)2,KH2PO4) and afterward the K2CO3 and see what the effect is.

Cheers,
Michael


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## Happi (17 Jan 2022)

MichaelJ said:


> Your absolutely right @Wookii,  My answer would be that I want that little bit of buffering that 1-2 KH would give in terms of stabilizing my pH... But I am definitely not 100% sure if I really, really need it.  If I would think enough about it, I would ask myself why would my pH not be stable ? what could possibly cause "severe" pH swings in a healthy well-maintained low-tech tank, and would said swings even be an issue for my plants or livestock?
> 
> 
> 
> ...


kept the 0 KH for decade now and am confident enough to say that you are more likely to kill your stock with overdose of CO2 rather than the 0 KH. you can expect the PH to stay between 5-6 and I have never seen it crash

here is a good discussion about the KH and PH: KH and plants


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## arcturus (17 Jan 2022)

Several commercial remineralization salts claim that they do not change the pH while raising the GH and KH. Given the discussion in this thread, how is this possible? Are these remineralizers using additional substances to neutralize the alkalinity increase? Or are they using other salts to increase GH and KH that have a minor effect on pH? (sorry for the dumb question, but I am not a chemist).


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## dw1305 (17 Jan 2022)

Hi all,


arcturus said:


> they do not change the pH while raising the GH and KH


You can add dGH without raising the pH, using a <"neutral salt"> like calcium chloride dihydrate (CaCl2.2H2O). The only way you could add dKH without raising the pH is if the pH was already at the CO2 ~ HCO3 ~ pH equilibrium point of ~pH 8.  Once you get more than about 2dKH the pH will always return to ~pH 7.8 ish, because the solubility of calcium carbonate (CaCO3) is dependent upon the amount of atmospheric CO2. 


arcturus said:


> Are these remineralizers using additional substances to neutralize the alkalinity increase


If you added an acid as well, it <"would counteract the addition of dKH">, but by turning the added <"DIC / TIC from HCO3- to CO2">, which would then out-gas, so the net effect would be that you haven't actually added any dKH. 

cheers Darrel


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## MichaelJ (17 Jan 2022)

Happi said:


> kept the 0 KH for decade now and am confident enough to say that you are more likely to kill your stock with overdose of CO2 rather than the 0 KH. you can expect the PH to stay between 5-6 and I have never seen it crash


Thanks @Happi  Since I don't inject, I don't have to worry about that part.  Speaking about _crashes -_ its a very vague concept IMO. What actually constitute a crash?  On a daily basis the CO2 injectors are forcing a 1 - 1.5 pH drop (thats a 10-50 times change in acidity level!) over the course of 6-8 hours, so that seems to counter the general idea of the importance of pH stability... (you see a similar change in some natural habitats with low alkalinity), but I suppose the relative drop vs. the timeframe within the drop occurs may play the biggest role here. So along that line of reasoning, _crashes_ happening out of the blue, without introducing any compounds that would drastically alter the water chemistry, in a well kept tank seem like a very unlikely event to occur. What I am worried about is the general pH level being too low. The 5-6 range would be too low for my shrimps. So having that little bit of buffering in the 1-2 KH range is likely a good idea in my case if that helps maintain the equilibrium towards the 6-7 range.

On a sidenote: I went ahead and made the WC yesterday using the K2CO3 and the rest of my minerals mixed in. When I tested in the evening my pH was 6.5-6.7 which is very close to what it was before the WC and my KH was about ~1 KH.  My TDS is now down at ~180ppm. The next couple of 40% WC's should bring this particular tank down to the mid 150 ppm range which is probably the lowest level I can expect with the chemical markup of my WC water. I will try and see if I can replace at least some of the CaSO4 with Ca Gluconate, to cut back on the SO4, without the Ca Gluconate turning my water into _skim milk _

Cheers,
Michael


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## MichaelJ (20 Jan 2022)

MichaelJ said:


> I will run an experiment where I start adding all my minerals and salts (MgSO4,CaSO4,Mg(NO3)2,KH2PO4) and afterward the K2CO3 and see what the effect is.
> 
> Cheers,
> Michael


Hi @dw1305  I ran this experiment today. Adding all the minerals and salts and letting it dissolve before adding the K2CO3 made the pH for the 2.0 KH target somewhere between 7.5-8... definitely nowhere near 9 pH or above as in my original experiment with pure RO and K2CO3 only.  So for my purpose, given my low ~1.5 KH target, the use of K2CO3 seems to fit the bill for now.

Cheers,
Michael


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