# KH <= GH



## Edward Shave (19 Nov 2018)

A short time ago A thread I started in another place was closed down by a moderator because I was arguing that KH can never be greater than GH. In fact the moderator went so far as to say this was nonsense.

Now this really threw me because I'm sure I'm right....

Since I'm posting this in the "Water Chemistry" section I'm hoping some knowledgeable person will confirm this and thus save my sanity lol.


----------



## ian_m (19 Nov 2018)

Can't see any deleted/closed post by you. All posts & threads by you are still open and active (or not).


----------



## Edward Shave (19 Nov 2018)

Apologies, I should have been clearer... By another place I meant a different site altogether.


----------



## Andrew Butler (19 Nov 2018)

Edward Shave said:


> Now this really threw me because I'm sure I'm right....


A quick google of 'KH greater than GH' will give you your answer and I'm afraid to say it seems you might be wrong 

A 'reliable' source:
https://www.jbl.de/en/blog/detail/341/why-is-the-kh-higher-than-the-gh


----------



## Nuno Gomes (19 Nov 2018)

Edward Shave said:


> A short time ago A thread I started in another place was closed down by a moderator because I was arguing that KH can never be greater than GH. In fact the moderator went so far as to say this was nonsense.
> 
> Now this really threw me because I'm sure I'm right....
> 
> Since I'm posting this in the "Water Chemistry" section I'm hoping some knowledgeable person will confirm this and thus save my sanity lol.



If you are sure, why do you need someone to confirm you're right?

And you're wrong by the way, but I do understand the mixup, the General in GH makes people think GH includes KH.....


----------



## Edward Shave (19 Nov 2018)

Andrew Butler said:


> A quick google of 'KH greater than GH' will give you your answer and I'm afraid to say it seems you might be wrong
> 
> A 'reliable' source:
> https://www.jbl.de/en/blog/detail/341/why-is-the-kh-higher-than-the-gh



Many people including the author of this article make no distinction between KH and Alkalinity..! They are not the same. Alkalinity can indeed be greater than GH but KH cannot since GH=KH+NKH.


----------



## Edward Shave (19 Nov 2018)

Nuno Gomes said:


> If you are sure, why do you need someone to confirm you're right?
> 
> And you're wrong by the way, but I do understand the mixup, the General in GH makes people think GH includes KH.....



GH is Total Hardness. Total hardness = Carbonate hardness (KH) + non Carbonate hardness.


----------



## Nuno Gomes (19 Nov 2018)

It's General Hardness, not Total Hardness.


----------



## Edward Shave (19 Nov 2018)

Nuno Gomes said:


> It's General Hardness, not Total Hardness.



Should more accurately be called “Total Hardness” as it was mistranslated from the German “Gesamthärte“. The term “Total” makes more sense as GH is the sum of carbonate and non carbonate hardness


----------



## Daveslaney (19 Nov 2018)

Edward Shave said:


> GH is Total Hardness. Total hardness = Carbonate hardness (KH) + non Carbonate hardness.


Sorry to say but I think you just answered your own question here.
GH= KH PLUS NON CARBONATE HARDNESS. So there for the KH can never be greater than the GH.
But according to the link provided by Andrew GH is actually just the magnesium and calcium.
So the KH can be higher than the GH.


----------



## X3NiTH (19 Nov 2018)

Semantics!

Total Hardness = Permanent Hardness + Temporary Hardness

Permanent Hardness = Chlorides + Sulfates etc.

Temporary Hardness = Carbonates

Total = All Ions (not just Ca and Mg)
Permanent = Not removed by boiling
Temporary = Removed by boiling


----------



## Edward Shave (19 Nov 2018)

X3NiTH said:


> Semantics!
> 
> Total Hardness = Permanent Hardness + Temporary Hardness
> 
> ...



The "Temporary Hardness" you refer to in your first equation is another name for Carbonate Hardness or KH. So by your definition KH must be less than Total Hardness (GH).

Strictly speaking Total Hardness is the sum of multivalent cations so for example monovalent ions such as Na+ (sodium) are not included.


----------



## Edward Shave (19 Nov 2018)

Daveslaney said:


> Sorry to say but I think you just answered your own question here.
> GH= KH PLUS NON CARBONATE HARDNESS. So there for the KH can never be greater than the GH.
> But according to the link provided by Andrew GH is actually just the magnesium and calcium.
> So the KH can be higher than the GH.



GH or total hardness is a measure of the multivalent cations present in the water. Principally Ca++ and Mg++

KH or carbonate hardness is that portion of GH cations associated with carbonate/bicarbonate anions. Despite the name it is the multivalent cations and not the carbonate anions that contribute the hardness property.

NKH or non carbonate hardness is the remainder of the multivalent cations not associated with carbonates.

Thus GH=KH+NKH leading to the conclusion that KH<=GH


----------



## NOWIS (19 Nov 2018)

Is an aquarium gh test affected by carbonates?


----------



## dw1305 (20 Nov 2018)

Hi all, 





Edward Shave said:


> GH or total hardness is a measure of the multivalent cations present in the water. Principally Ca++ and Mg++ KH or carbonate hardness is that portion of GH cations associated with carbonate/bicarbonate anions. Despite the name it is the multivalent cations and not the carbonate anions that contribute the hardness property.


This is all in the the OP's (@Edward Shave), other thread, <"Boiling off KH">.





X3NiTH said:


> Total Hardness = Permanent Hardness + Temporary Hardness
> 
> Permanent Hardness = Chlorides + Sulfates etc.
> 
> ...


That one. When you add a monovalent carbonate (like sodium bicarbonate (NaHCO3)) you have raised the carbonate hardness (dKH), electrical conductivity (you've added Na+ and HCO3- ions), pH and the alkalinity, but you haven't raised the dGH, because you haven't added a multivalent cation.

The best summary of water hardness I've found are still the ones on "the Krib" <"Water Hardness"> and <"Hardness (incl. History">, mainly because they include the history and definition of the units. 

A definition of "Total Hardness" is here: <"Total Hardness">

cheers Darrel


----------



## zozo (20 Nov 2018)

Latest Water company report.. 





My test kit averagely results in 11 - 12 dKh slight color switch starts at 10.

1 dKh = 17,86mg/l  HCO3 190,38/17.86 = 10,66

This is an average report it fluctuates between 190 and 210 mg/l HCO3 (but did cut that out off the report to make the image smaller), test kit is pretty accuratly coresponding the WC report.

My Gh test results is 6°dH,  1 mmol/l = 5,62 ºdH.. Coresponds with above 1,09 mmol/l

1°dH = 10mg/l CaO or 10mg/l MgO
Dunno how that corresponds with the above 32,29 mg/l Ca and 7,53 mg/l Mg i'm missing an O there and the knowledge.

But what we can read from the test kits it seems my kH has a higher number than my gH..


----------



## Edward Shave (20 Nov 2018)

dw1305 said:


> ...When you add a monovalent carbonate (like sodium bicarbonate (NaHCO3)) you have raised the carbonate hardness (dKH)...



You are right, sodium bicarbonate will raise the value of KH but not beyond GH. What your really doing is raising the alkalinity and the two values are the same so long as KH < GH. Alkalinity on the other hand can be greater than GH.


----------



## Edward Shave (20 Nov 2018)

zozo said:


> ...But what we can read from the test kits it seems my kH has a higher number than my gH.. ...



Your test kit is measuring Alkalinity (A) not KH. A = KH so long as KH<GH. If A>GH then KH=GH.


----------



## Edward Shave (20 Nov 2018)

dw1305 said:


> This is all in the the OP's (@Edward Shave), other thread, <"Boiling off KH">


I don't think that thread is a good example as it contains a number of inaccuracies.


----------



## zozo (20 Nov 2018)

Edward Shave said:


> Your test kit is measuring Alkalinity (A) not KH. A = KH so long as KH<GH. If A>GH then KH=GH.



I know that both tets are determined by adding acids and the amount of drops reflects in a pH change again in a color change. 

I didn't reply to discuss the issue i don't posses the knowledge i can't argue nor agree, just thought to give an example from my personal situation, that my tap water measeres kH 10 value, a higher number than the gH 6 value. Considered hard in carbonates and soft in CA and Mg.

But obviously i'm far from understanding yuor question and point.. Sorry..


----------



## Edward Shave (20 Nov 2018)

zozo said:


> ut obviously i'm far from understanding yuor question and point.. Sorry..



Hi Marcel
Sorry if my answer seemed a little kurt as it wasn't intended that way.
The test kit manufacturers must share a lot of the blame for the confusion. It is relatively easy to measure Alkalinity (A) but not so easy to measure KH. Since A=KH so long as KH<=GH and since this is the case for the vast majority of us aquarists the easy answer is to label the Alkalinity test as KH. In fact my "KH" test kit label also contains the word alkalinity in smaller print.
Your case is an example of why I think it's worth knowing the difference.


----------



## Edward Shave (20 Nov 2018)

Simon Hellmich said:


> Is an aquarium gh test affected by carbonates?



No. At least that goes for the NT Labs test kit I use.


----------



## zozo (20 Nov 2018)

But still the alkalinity test result i get from that drop test is pretty spot on compaired next to the water company laboratory method in measuring mg/l HCO3
Then i may expect that there is a accurate corelation in bot methods i can recalculate it back to same results.. Assuming the laboratory uses a different method than acid based tittation and convert it with a wet finger into mg/l HCO3 on their report.

And reading this forum a lot i noticed the majority in the UK averagely has a higher Gh than kH, but where i'm from its other way around. That is actualy what i wanted to show.. That's all. I do not understand all chemistry behind it enough to go into it any further than basic knowledge and formulas. There surtainly will be exceptions not explained in the basics.

All i have is a laboratory report and some simple home tests and both come up with pretty accurae summilar values if i recalculate it with what i know. Huh? always forget and can look back up i mean..


----------



## Edward Shave (20 Nov 2018)

zozo said:


> And reading this forum a lot i noticed the majority in the UK averagely has a higher Gh than kH, but where i'm from its other way around. That is actualy what i wanted to show.. That's all.



Hi again Marcel. 
I have no argument with your figures which I'm sure are correct. I'm sure also that you are correct to say that KH (as measured by your test kit) is greater than GH in your area.

addendum
I just noticed your water company is reporting total carbonates not carbonate hardness. So again this figure refers to alkalinity.


----------



## zozo (20 Nov 2018)

Hi Edward, 

I believe your word for it.. Dunno what that all means.. 

I thought to understand since 1° dKh equals 17.86 mg/l carbonate and bicarbonate which obviously has a coralation with alkilinity there aint much to argument.

But obviously that seems not the whole story.

Interesting.


----------



## dw1305 (20 Nov 2018)

Hi all,





Edward Shave said:


> I don't think that thread is a good example as it contains a number of inaccuracies.


I don't think it does, which bits are inaccurate? I've just looked back through it, and the science is right and it additionally mentions the ICP analysis that is in Marcel's water report etc. 





Edward Shave said:


> What your really doing is raising the alkalinity and the two values are the same so long as KH < GH. Alkalinity on the other hand can be greater than GH


Alkalinity doesn't directly relate to either dGH or dKH, because other ions and compounds are also bases. Alkalinity is the ability of a solution to resist pH change when acids are added, so it is a measure of <"buffering">. Acids are "proton (H+ ion) donors" and bases (alkalis) are "proton acceptors".

In water you usually have carbonate buffering, but you can have other buffered systems like <"sodium phosphate buffers">, where disodium phosphate (Na2HPO4) is a base, and sodium dihydrogen phosphate (NaH2PO4) the acid.  You can tell which is which from the formulae, the base has two alkali metal atoms which will both become Na+ in solution and the acid has one H+ and one Na+. Sodium citrate/citric acid etc are other buffered systems.





Edward Shave said:


> It is relatively easy to measure Alkalinity (A) but not so easy to measure KH.


That is right, test kits use alkalinity as a proxy for hardness, because usually, in tank water, they are both derived from limestone and the alkalinity and hardness (both dKH and dGH) are linked if both derive from CaCO3, but they aren't if they originate from other salts. 





Edward Shave said:


> You are right, sodium bicarbonate will raise the value of KH but not beyond GH


*It can.*

<"Group I (alkali metal) carbonates are *soluble">, *the solubility of NaHCO3 is 96 g/L (20 °C) in H2O.  When you add NaHCO3 you raise dKH, but not dGH, you haven't added any dGH (multivalent cations). If you add NaHCO3 (Na+, HCO3-) to a solution which is already saturated with Ca++ and HCO3- ions, CaCO3 will precipitate out, CaCO3 is less soluble than NaHCO3.

The salts of all group I metals are soluble, many of the salts of group II metals (Ca, Mg etc.) are not, as an example the solubility of CaCO3 is 0.013 g/L (25 °C).

cheers Darrel


----------



## Edward Shave (20 Nov 2018)

dw1305 said:


> I don't think it does, which bits are inaccurate? I've just looked back through it, and the science is right and it additionally mentions the ICP analysis that is in Marcel's water report etc



When I get a minute I'll go back to the original thread and try to point out the inaccuracies.



dw1305 said:


> Alkalinity doesn't directly relate to either dGH or dKH



My point exactly..!

I think the main difference between us lies in how we define KH

I think we both agree that GH is the sum of multivalent cations or total hardness
These cations must be balanced by an equal amount (in terms of charge) of anions
Historically it was found convenient to divide these cations into two groups, those balanced by carbonate anions KH and those balanced by other anions. So KH is that portion of GH balanced by carbonates.
If there are enough carbonates present to balance all the hardness then KH=GH. Increasing the supply of carbonates beyond this point will have no effect on KH as all the cations have already been used up.


----------



## dw1305 (20 Nov 2018)

Hi all, 





Edward Shave said:


> These cations must be balanced by an equal amount (in terms of charge) of anions


They must.





Edward Shave said:


> So KH is that portion of GH balanced by carbonates.


It is the amount of carbonate buffering, it doesn't matter which compound the HCO3- ions have come from. In solution an ion is an ion is an ion, they are all the same. 





Edward Shave said:


> Increasing the supply of carbonates beyond this point will have no effect on KH as all the cations have already been used up


Not exactly, it is back to the differing solubility of the (periodic table) group I "alkali metal" elements and the group II "alkaline earth" elements, and the <"common ion"> effect. 

You can have *a lot *of Na+ and HCO3 ions in solution, we know this because of the high solubility of sodium bicarbonate (or sodium carbonate (Na2CO3)) in water. You can also see why sodium carbonate is a stronger base than sodium bicarbonate (sodium carbonate has two sodium atoms (Na+ ions)). 

If you add Na+ and HCO3- ions to water, which is already saturated with Ca++ and HCO3- ions (and at 400 ppm CO2 a very small weight of CaCO3 dissolves), you will always get CaCO3 precipitated out, because it is the least soluble carbonate. You used up all the Ca++ ions, but you still have plenty of Na+, HCO3- ions and H2O molecules (the water). 

The H2O can surrender a H+ ion (to the CO3--), creating both a HCO3- and an OH- ion (H2O - H+ = OH-) and raising the pH. 

cheers Darrel


----------



## Edward Shave (20 Nov 2018)

dw1305 said:


> It is the amount of carbonate buffering



No, it is that portion of GH balanced by carbonates.



dw1305 said:


> Not exactly, it is back to the differing solubility



This is just plain wrong. It's much simpler than you make it out to be. 
But if you wont take my word for it maybe a couple of citations will help...

From...WATER CHEMISTRY
An Introduction to the Chemistry of Natural
and Engineered Aquatic Systems
Patrick L. Brezonik and William A. Arnold
Page 377
"Hardness, the sum of multivalent cations in water, usually is dominated by Ca2+ and Mg2+. The carbonate hardness is that portion of the hardness that can be associated with the bicarbonate and carbonate present in the water.

From... FRESHWATER AQUARIUM CHEMISTRY
Kevin J Ruff PhD
Page 38
General hardness is comprised of two parts 1) "Carbonate Hardness" (KH), and 2) "Non Carbonate Hardness" (None KH or NKH). The K in KH comes from the German spelling of carbonate.) So.... GH=KH+NKH


----------



## dw1305 (20 Nov 2018)

Hi all,
@Edward Shave, we are just going around in circles, and we will have to differ in our view.

"Degrees of hardness" are strange terms, scientists don't tend to use them, they look at elements in solution (ions) in mols or ppm (mg/L) and alkalinity in milliequivalents/L, but the definition of dKH is:

 "_One German degree of carbonate hardness (dKH) corresponds to the carbonate and bicarbonate ions found in a solution of approximately 17.848 milligrams of calcium carbonate (CaCO3) per litre of water (17.848 ppm). Both measurements (mg/L or KH) are usually expressed "as CaCO3" – meaning the concentration of carbonate expressed as if calcium carbonate were the sole source of carbonate ions. Bicarbonate ions only contribute half as much carbonate hardness as carbonate ions, so bicarbonates that are present in the water are converted to an equivalent concentration of carbonates when determining KH_."

I'm pretty sure it doesn't matter where the carbonate/bicarbonate ions came from, we are expressing them in terms of CaCO3 (derived from CaO), but they don't have to originate from CaCO3.

This is via <"Wikipedia"> "_An aqueous solution containing 120 mg NaHCO3 (baking soda) per litre of water will contain 1.4285 mmol/l of bicarbonate, since the molar mass of baking soda is 84.007 g/mol. This is equivalent in carbonate hardness to a solution containing 0.71423 mmol/L of (calcium) carbonate, or 71.485 mg/l of calcium carbonate (molar mass 100.09 g/mol). Since one degree KH = 17.848 mg/L CaCO3, this solution has a KH of 4.0052 degrees_.">

cheers Darrel


----------



## Edward Shave (20 Nov 2018)

I think this might help also...
https://www.emdmillipore.com/Web-US...mentType=PI&Language=EN&Country=NF&Origin=PDP


----------



## Edward Shave (20 Nov 2018)

dw1305 said:


> "_One German degree of carbonate hardness (dKH) corresponds to the carbonate and bicarbonate ions found in a solution of approximately 17.848 milligrams of calcium carbonate (CaCO3) per litre of water (17.848 ppm). Both measurements (mg/L or KH) are usually expressed "as CaCO3" – meaning the concentration of carbonate expressed as if calcium carbonate were the sole source of carbonate ions. Bicarbonate ions only contribute half as much carbonate hardness as carbonate ions, so bicarbonates that are present in the water are converted to an equivalent concentration of carbonates when determining KH_."



I don't disagree with any of that but what does it have to do with the definition of KH?



dw1305 said:


> I'm pretty sure it doesn't matter where the carbonate/bicarbonate ions came from, we are expressing them in terms of CaCO3 (derived from CaO), but they don't have to originate from CaCO3.



I don't disagree with that either but I never suggested it matters where the carbonates came from.

I would just like to say how much I appreciate your input even if we don't agree.


----------



## Edward Shave (20 Nov 2018)

So is there no one who agrees with me?

I find it fascinating that this misconception regarding KH is so ingrained in the hobby..!


----------



## zozo (20 Nov 2018)

Edward Shave said:


> I find it fascinating that this misconception regarding KH is so ingrained in the hobby..!



Depends on where you put the focus, the hobby is still quite devided....  For most of the oldschool hobbyist still not dissolved into the the CO² hype actualy don't give a flyig figure about kH.


----------



## dw1305 (20 Nov 2018)

Hi all, 





Edward Shave said:


> I find it fascinating that this misconception regarding KH is so ingrained in the hobby


I agree it would make much more sense to actually stop using "dGH" & "dKH", and use non-ambiguous units like mg/L. 

If test kits referred to alkalinity, rather than carbonate hardness, it would also make things more transparent. In most UK waters the alkalinity, dGH and dKH all come just from dissolved CaCO3, and they are all clearly correlated with one another. 

This isn't true universally and a water body like <"Lake Tanganyika"> would have very different chemistry. 

cheers Darrel


----------



## Konsa (20 Nov 2018)

Hi
I dont have the knowledge to get involved in the discussion but I find it fascinating too  as I don't  even bother testing my KH or GH  or anything else (apart from PH for the CO2 profile when I was high tech)in my tanks for the last 6 years and my hobby is so much more enjoyable.I have what I have in my tap and the rest is just waterchanges, waterchanges and if I haven't mentioned it before more waterchanges. 
P.S. Please don't get me wrong as writen text is easily misunderstood. I dont mean to be rude and at the end of the day I may even learn sth new too.But overcomplicating things is not really my thing.
Kind Regards 
Konsa


----------



## jcspotless (1 Dec 2018)

Hi,
I am new to this forum and finding it interesting this discussion on GH and KH. I am a analytical chemist by training so I think I know a little bit about water chemistry. My question is this: It seems to me that KH should be kept high if you want pH stability since this is a buffer. However low GH and KH seem to be what a lot of people are aiming for. I do not really get that. Why would you want to remove something which stabilises your pH?

I can understand if want to change pH that you would want a low KH so you can change it. But when you get to your target pH, why would you not want to again have a high KH. I have not read anything concrete to suggest high KH per se is a bad thing.

Am I missing something?


----------



## zozo (1 Dec 2018)

jcspotless said:


> Am I missing something?



No not realy and if you want to keep an aqaurium long term, something like a low energy Wallstad setup with a minimum of water changes than a good buffer might be more important.

In the nowadays High Tech CO² era, metaphoricaly the Sports Car Setup among planted aqauriums, preferably metabolising at top speed, fuelled to the max with EI. Needs a lot more maintenance and water changes to flush out and delute build up organic waste products and excess ferts to maintain a form of stability and give it a weekly reset. Averagely at least 50% weekly is adviced with a proper substrate vacuum to get rid of decaying materials. That way you actualy prevent an accumulation of substances that possibly could influence pH negatively other than the CO² you're pumping in.

I'm not 100% sure someone will correct if i'm wrong anyway   But if i remember correctly that a Higher kH than ideal (> kH 6) can prevent certain fert ellements comming out of solution. For example Iron is such an ellement, than running an aqaurium at such high metabolic speed you might run into deficiencies. Something to do with Calcium staying in solution due to the CO² added counteracts Fe ions to come available for the plants. At least i believe it was something along that line..

Than we actualy provide the needed stability with maintence and husbandry and don't need to rely on the waters kH buffer capacity regarding a buildup in organic acids.

And if i rember correctly also for low energy setups the pH has an effect on micro elements comming out of solution and available to plants. For example i have kH 10 and a high alkalinity my average pH profile is pH 8 +.. Also not ideal and could run into Fe deficiencies if i grow plants that require more of this. Than a lower alkalinity gets easier to maintain a more ideal pH value.

This higher alkalinity also prevents me ever from keeping fish that require a lower pH.. LIke some apistos.. It's very hard to get a lower required pH with a dkH 10 water


----------



## Oldguy (1 Dec 2018)

dw1305 said:


> The best summary of water hardness


As you say its in the history, especially the determination of 'hardness' with a standard soap solution and scum/lather formation. Hate terms such as kH & gH, always have to look them up. Much prefer ppm and the substance of interest. Terminology also muddied by assuming all waters are natural and using Ca2+ as an industrial short hand. The water in our little glass boxes is anything but natural especially if you follow the EI path.


----------



## dw1305 (1 Dec 2018)

Hi all,





Oldguy said:


> Hate terms such as kH & gH, always have to look them up. Much prefer ppm and the substance of interest. Terminology also muddied by assuming all waters are natural and using Ca2+ as an industrial short hand


It would make a lot more sense. 





jcspotless said:


> My question is this: It seems to me that KH should be kept high if you want pH stability since this is a buffer. However low GH and KH seem to be what a lot of people are aiming for. I do not really get that. Why would you want to remove something which stabilises your pH?


 That is it. The carbonate hardness (which we use dKH as units for) stabilises the pH at ~pH 8  via the CO2/carbonate equilibrium (assuming ) 400ppm atmospheric CO2. The total amount of inorganic carbon (TIC/DIC) remains the same, it form just changes dependent upon pH.  When you add CO2 you depress the pH, because you've added H2CO3, and that is a proton donor (the "spare" H+ ion). 

If you keep hard water fish (lake Tanganyika cichlids etc.) or hard water plants (_Vallisneria_ etc.) they have evolved in carbonate rich water and have adaptations for this environment. Plants like _Vallisneria_ etc. have the physiological pathways to use bicarbonate (HCO3-) as a carbon source in photosynthesis and to efficiently sequester nutrients like PO4 --- and Fe+++, which are of very limited in their availability in hard water.  They also often don't have any mechanisms for avoiding iron toxicity in reducing or acidic conditions.

The pH stability of hard water isn't as set in stone as many people suggest, mainly because <"in vegetated water there will always be diurnal swings in pH"> caused by the differing CO2:O2 ratio during (and after) photosynthesis. In carbonate buffered water the amplitude of the swing will be much reduced.

Most commonly kept fish and plants don't have any particular water requirements, and will live and reproduce in a range of water types. In very hard water a lot of plant nutrients are less available and high levels of Ca++ ions may interfere with the uptake of Mg++, Fe+++ and K+ ions, and bio-calcification.

A limited number of plants and fish come from water without any natural carbonate hardness, this includes many of the "black-water" fish from SE Asia (_Parosphromenus_ spp.) and the central Amazon basin (_Dicrossus filamentosus etc._), and plants like _Syngonanthus_ & _Tonina_ and _Brasenia _species. These plant and fish can only be maintained long term in soft, acid, nutrient poor water. The exact reason for this is not fully known, but may relate to their efficiency in obtaining scarce cations in their natural habitat, and problems with an excess of these elements when they are more available.

Does any of this matter? <"Views on this forum vary">.

cheers Darrel


----------



## Oldguy (1 Dec 2018)

jcspotless said:


> want pH stability since this is a buffer.


Most plant enthusiasts want 'free CO2' in their tanks so that non obligate aquatic plants can grow well under water. We blow CO2 into the water to feed the plants and try not to gas the fish. High buffering at pH 8 ish makes this difficult to achieve. Lower buffering at pH 8 or lower enables more CO2 to be 'free' especially at pH 6.8 and lower and lower buffering enables this to be achieved. This buffering is typically expressed as bicarbonate buffering but in practice is the sum of a thousand and one different ions. Eg the aqueous sulphate ion has a pH of about 7.4. The planty folk also pour dihydrgen phoshates into their tanks which will dissociate into both mono and di salts and form a strong pH buffer. Rain water and purer has little buffering capacity but the water in our little glass boxes has.


----------



## Edvet (1 Dec 2018)

jcspotless said:


> if you want pH stability


pH swings due to CO2 is a weak acid reaction, these are virtually harmless to our animals. Wanting to keep pH constant can lead to dangerous measures.


----------



## sciencefiction (1 Dec 2018)

zozo said:


> This higher alkalinity also prevents me ever from keeping fish that require a lower pH.. LIke some apistos.. It's very hard to get a lower required pH with a dkH 10 water



Not a chemist but from my own research on the same:

*Total Alkalinity* = [HCO3-] + [OH-] - [H+]

Total alkalinity(buffering capacity), is not directly related to dGH.

On another hand pH is expressed via the formula  [H+] = 1x10^-pH which means the more [H+] in the water, the lower the pH, the lower the alkalinity. The higher the [HCO3-] + [OH-] , the higher the alkalinity, the higher the [OH-], the higher the pH.

*German Carbonate Hardness* or *dKH* = [HCO3-] +[CO3^2-]

or it is expressed in ppm of CaCO3 and is directly related to dGH in the meaning that dKH cannot be higher than dGH because dKh is part of the measurement of dGh


----------



## sciencefiction (1 Dec 2018)

Edvet said:


> pH swings due to CO2 is a weak acid reaction, these are virtually harmless to our animals. Wanting to keep pH constant can lead to dangerous measures



Following my above post, adding CO2 to water generates

1) CO2 + H2O <=> H2CO3
2) H2CO3 <=>[ H+] + [HCO3- ]

It does decrease pH due to the addition of [H+], however, it does not alter total alkalinity because it results in equal [H+] and [HCO3-] cancelling each other. It is the reason why fish are not bothered by swings of pH due to addition of CO2. However, fish would be affected by a massive drop of total alkalinity or when you have high [ H+]  concentrations and low or non-measurable [HCO3-] + [OH-] (for example adding strong acids) , meaning your water is non-balanced and totally out of whack....So in essence, you do want a measurable total alkalinity or what we've become to know as KH,  which naming isn't technically correct. as explained in my previous post, but regardless of its name, one should aim at some measurable level in the tank....


----------



## zozo (1 Dec 2018)

sciencefiction said:


> or it is expressed in ppm of CaCO3 and is directly related to dGH in the meaning that dKH cannot be higher than dGH because dKh is part of the measurement of dGh



What draws me off in this view is my water company report.. 
They measure HCO3 in mg/l, Total hardness in m/mol, not in the report but via an other route on the website i can lookup the dGh
 and they give a dGh 6 on my adress.

If i look up how many mg/l = 1 dKh is correponds with the report
Same as how many m/mol is 1 dGh corresponds with the report.
In this sum the result is a Higher Kh than Gh.

If the statement if dKh is higher than dKh = dGh than my water company is taking me for a ride and i do not have soft water. Than their website should simply say i have 10dGh but they don't...

I'm not confident enough in the matter to give the water company a call to dispute their report.. But i know a Chemsitry teacher... And i saw and asked him yesterday what he tought about the statement.. He looked at me with googly eyes and couldn't answer it straight away.. He said something like it's the way you look at it but it still are different things.. So there probably is no straight answer.. Or it is to difficult and boring to explain while playing a game of cards.


----------



## sciencefiction (1 Dec 2018)

zozo said:


> They measure HCO3 in mg/l, Total hardness in m/mol, not in the report but via an other route on the website i can lookup the dGh
> and they give a dGh 6 on my adress.



Where do you get dGH6 from?

From what I checked  mmol/l is converted to mg/l by multiplying the mmol/l value by the molecular weight of the component in grams so 1.09 mmol/l could be hundreds of mg/l.
From the way your report is presented, carbonate hardness is part of the that same total hardness of 1.09 mmol/l, which is the point in this thread.
So your water may not be that soft at all looking at that report...


----------



## zozo (1 Dec 2018)

sciencefiction said:


> Where do you get dGH6 from?



From my water companies website.. 
And a drop tester gives fairly the same result.

If i send my water company an e-mail they send me the latest lab report. In this report no gH is mentioned, they state total hardness in mmol/l

https://en.wikipedia.org/wiki/DGH


> 1 dGH is equivalent to 0.17832 mmol per litre of elemental calcium and/or magnesium ions



My WC Report - Total hardness = 1.09 mmol/l / 0.17832 = 6.1 dGh.. 

all this with 190mg/l HCO3  which equals 10 dKh.. Kh drop tester gives me the same result..

Than if the statement is true Kh = Gh than my water company is juggling and hussling with numbers to present their water softer than it realy is..


----------



## sparkyweasel (1 Dec 2018)

I think water companies only consider calcium and magnesium as hardness. And carbonate as alkalinity if they bother about it at all.


----------



## jcspotless (2 Dec 2018)

sparkyweasel said:


> I think water companies only consider calcium and magnesium as hardness. And carbonate as alkalinity if they bother about it at all.



I suspect the water company reports reflect the test methods in place. I have not worked for water company but have conducted analysis for bicarbonate (HCO3). I don't know what current methodology is but a quick google seems to imply they still use the traditional titration method for alkalinity for KH whereby a strong acid (HCL) is titrated to a fixed pH inflection point pH 4.5 to represent amount present is this then converted to units equivalent to millimolar of a given ion (HCO3). There are method to measure anions in solution directly (such as ion chromatography) but these have the disadvantage of being specific for target ions whereas the more traditional methods do not differentiate between the various anions which might be present. As sparkyweasel says total hardness may just be a measure of Cations (Mg and Ca) but expressed in units of mole equivalents of CaCO3 (mole weight 100.09)


----------



## jcspotless (2 Dec 2018)

Attached is water report from Affinity Water. It shows a hardness value of 330 (units mg CaCO3)/L) and Calcium value 132 (mgCa/L) . These two values may derived have same route value since difference between 330 and 132 is same as difference in formula weight (100.09 CaCO3 vs 40.078 Ca). In fact report says a single sample collected for each. I guess my point here is these values shouldn't be taken too literally as I suspect they are derived values based on requirement of analytical methods in place. Interesting I could not find published methods, it looks like to me. Its the ISO standards which (or their local equivalents, e.g BS std in UK) which are followed. I did find an old Swedish ISO standard which does provide some detail on how alkalinity method works. Attached for those interested. Current ISO std is version 2 not 1 but hopefully basics are still the same.


----------



## jcspotless (2 Dec 2018)

Edvet said:


> pH swings due to CO2 is a weak acid reaction, these are virtually harmless to our animals. Wanting to keep pH constant can lead to dangerous measures.



I can see how people may attempt to modify pH which they believe is effecting fish or plants. Surely a buffered system (with high ionic strength) will return to the pH pretty quickly to a pre-determined set point. Phosphate buffers at around pH 7. Bicarbonate higher. Injections of CO2 might change the equilibrium but if the ionic strength is high enough these anions will return the pH to a set point which is determined by the pKa of the substances in solution. Absence of the buffers (phosphate, carbonate etc) i.e a lower KH will lead to CO2 rapidly changing the pH. Hence my statement why does anyone want low KH. The concentration of CO2 and its ionic equivalent in solution can still be high (and presumably feed the plants). Given the very low concentrations of other elements Fe etc again I struggle to see a downside. Fish I assume do not like change in water conditions but how affected are they by hardness, I am skeptical. Maybe the ratio of Calcium and Magnesium is significant? Since calcium and magnesium might be biological involved in same processes I can understand how this may affect living systems. In low calcium and magnesium systems how to fish maintain a healthy blood chemistry (another argument for high KH ?)

Interested to hear opinion or better still facts.


----------



## Edvet (2 Dec 2018)

jcspotless said:


> why does anyone want low KH


   Reproducing the natural environment of many tropical fishes, though not always neccesary, can be better to induce breeding and /or replicate their natural behaviour. For instance blackwater habitats have low natural pH and very low conductivity. (ph range 4-5, <20 microsiemens).


----------



## Edvet (2 Dec 2018)

In Ukaps terms i believe having a pH controler influencing the CO2 delivery ( stryving for a constant pH) will lead to unstable CO2 levels, which will lead to algae. Having a pH drop from 1 point, which we generally advise in high light situations, is harmless for fish.
There is discussion wether the 1 point drop will be correlated to the same CO2 level in harder and softer water. I believe softer water will need higher drops, but others believe it doesn''t matter within the most used waterparameters.


----------



## dw1305 (2 Dec 2018)

Hi all,





jcspotless said:


> I can see how people may attempt to modify pH which they believe is effecting fish or plants. Surely a buffered system (with high ionic strength) will return to the pH pretty quickly to a pre-determined set point


It is the ionic strength that is the interesting bit, soft water has very few ions of any description, and any addition of weak acids (from dissolved CO2, humic compounds etc.) will reduce pH. If this water is vegetated then we have will have large diurnal variations in pH, because of the lack of carbonate buffering. There are values (and a scientific reference) in this thread <"TDS and remineralising.....">. 

You can start with low conductivity water and then replicate these conditions by adding humic substances. A good review article of this is <"All the leaves are brown">, this references Dr <"Christian Steinberg"> who is a leading researcher on the ecological role humic substances in fresh and marine water. 

If you start with hard water (high ionic strength) you can reduce the pH with an addition of acids, or you can buffer the pH to known value with phosphate (or citric acid/citrate) buffers, but you still end up with water with a high ionic strength (in fact you've added even more ions), but lower, or stable, pH. Long term experience of fish keeping has shown that this type of water is still unsuitable for the long term keeping and particularly breeding soft water fish.

As you approach pure H2O (rather than the weak salt solution, with H2O as a solvent, which we usually call water), pH becomes less and less meaningful as measurement, and because of this I'm more interested in conductivity, partially because it is linear scale from DI water to full strength sea water, and partially because a relatively cheap conductivity meter will give you an accurate reading without requiring calibration before every use etc.

If you want harder water things are a lot more straight forward, you just have to add calcium carbonate to raise the pH to a relatively stable pH8.

cheers Darrel


----------



## zozo (3 Dec 2018)

Edward Shave said:


> Should more accurately be called “Total Hardness” as it was mistranslated from the German “Gesamthärte“. The term “Total” makes more sense as GH is the sum of carbonate and non carbonate hardness



Not completely according how the Germans explain their view of Water hardness and how to interpret the term.

https://de.wikipedia.org/wiki/Wasserhärte

*Gesamthärte* -  GH- Total hardness = The concentration of cationes of <alkaline earth metals> in the water. Generaly Ca and Mg

*Carbonat-Härte* = KH = concentrations of Hydrogen Carbonates anions, the equivalent part of cationes of alkaline earth metals is the *Temporate Carbonate Hardness*. That's the Calcium carbonate - carbonic acid - carbon dioxide equilibrium. And if you heat it, CO² escapes and Calcium deposites.

They have a 3th one that is not commenly used so it doesn't realy come with an abriviation.(nKH?)

*Nichtcarbonat-Härte* - Non Permanent Carbonate Hardness or *Lasting Hardness* = The Total Hardness from anions that are not bound to Hydrogen Carbonates and can not be removed.

Somewhere in 2007 they realised the confusement it actualy gives and introduced new regulations of the hardness ranges.
in mmol/l

Am i correct to assume that only if KH is made up from equivalent cations T-KH than it is also GH?
But if i take for example Demineralized water (0 in any hardness) and only add Bicarbonates i add KH but no GH since i don't add any alkaline earth metals?

And that the confusement indeed is a mistranslation or more to say a misinterpretation of termology? (Gesamthärte = Total Hardness)


----------



## zozo (3 Dec 2018)

zozo said:


> Non Permanent Carbonate Hardness



Sorry that should be "Non Carbonate Permanent Hardness"..


----------



## zozo (3 Dec 2018)

Another one.. 




Obviously as a play of words maybe...  Even if certain elements physicaly are not present, than there still is a total hardness.. Thus if there is nothing to determine GH and KH is measured than KH is considered GH.

Found the red hering..


----------



## dw1305 (3 Dec 2018)

Hi all, 





jcspotless said:


> Fish I assume do not like change in water conditions but how affected are they by hardness, I am skeptical.


Depends on the fish, a lot of "soft water" fish can be maintained in hard water, but they often can't breed successfully. 

Some "black-water" fish can only be maintained in soft acid water. This may relate to their inability to survive in environments with a high bacterial load, because the acidic, oligotrophic habitats have a very limited, and specialised, microbiota. That is one reason why you get the build up of dead leaves and   woody material in black-water conditions, rates of decay are very slow.

In some cases the addition of humic compounds, particularly ones with ion-exchange capacity, can lead to successful egg hatching, although the exact mechanism isn't known. This technique is commonly used with cave nesting fish (like _Apistogramma megaptera_ and _Poecilocharax weitzmani_), where <"long strand sphagnum peat"> is inserted in the spawning cave, pre-spawning. With catfish like _Corydoras_ spp. and the more demanding L numbers, then <"Alder (_Alnus gutinosa_) "cones"> are often added to the spawning tank.  

It is thought that the high levels of dGH cause a toughening of the egg coat and this stops successful egg development.There may also be issues with "nephrocalcinosis", in fish although this can also be associated with elevated CO2 levels.





jcspotless said:


> In low calcium and magnesium systems how to fish maintain a healthy blood chemistry (another argument for high KH ?)


It is just because they evolved in situations with very low levels of alkaline, and alkaline earth, metal cations. Since the widespread use of RO units fish like Discus have been much easier to maintain. 

As a general rule you can't maintain hard water fish in soft water, but it is usually less of an issue, because it is much easier to add substances to water, rather than take them away. 

cheers Darrel


----------



## dw1305 (3 Dec 2018)

Hi all,


jcspotless said:


> I don't know what current methodology is but a quick google seems to imply they still use the traditional titration method for alkalinity for KH whereby a strong acid (HCL) is titrated to a fixed pH inflection point pH 4.5 to represent amount present is this then converted to units equivalent to millimolar of a given ion (HCO3).


I think they do.


jcspotless said:


> It shows a hardness value of 330 (units mg CaCO3)/L) and Calcium value 132 (mgCa/L) . These two values may derived have same route value since difference between 330 and 132 is same as difference in formula weight (100.09 CaCO3 vs 40.078 Ca). In fact report says a single sample collected for each. I guess my point here is these values shouldn't be taken too literally as I suspect they are derived values based on requirement of analytical methods in place.


They are.

The calcium value will sometimes differ, because it has been measured via ICP, but usually they are all derived units.

There isn't much magnesium in most British tap water,  <"for geological reasons">.  In the UK you can assume that alkalinity, dGH and dKH all relate directly to dissolved CaCO3. Conductivity is also mainly a reflection of geology, although if you live near the sea you may have salt water ingress.

This isn't true for New Zealand, <"or Lake Tanganyika">, where volcanic activity has led to very different water composition.

cheers Darrel


----------



## sciencefiction (3 Dec 2018)

zozo said:


> But if i take for example Demineralized water (0 in any hardness) and only add Bicarbonates i add KH but no GH since i don't add any alkaline earth metals?



Yes, because when you add soda bicarbonate, you only add [HCO3-] and [OH-], but not Ca2+ or Mg2+ , so dGH remains unchanged. But even when adding soda bicarbonate, you'll have a really hard time moving the KH up more than 4 dKH or so...It would take lots of soda bicarbonate  The pH will go up due to the addition of [OH-],, but then again....because GH is not changed, fish could not care one bit about the upward pH swing for that same reason,,, Hence pH is an irrelevant measure and it only matters as a guidance, to give a general idea of how hard one's water is...but on its own, without knowing the rest, it means nothing....In certain scenarios one can have high pH and soft water and low pH and hard water, although the opposite is true as well in majority of cases.

If you add soda bicarbonate to soft water, it will not make ones water any harder  because there's no Ca2+ or Mg2+ involved. However, adding soda bicarbonate means an addition of [OH-],which will level out the [H+] and bring the pH back up, thus balancing the water. It doesn't need to be balanced back to a neutral pH, it just means that there's enough [OH-] for the tank to function correctly. Old tanks tend to become acidic,....so addition of bases is essential, normally via water changes and not soda bicarbonate 

I have had a scenario when my pH plummeted down, KH zero-ed out, the GH remained unchanged, TDS was through the roof, fish were gasping...So I don't measure GH ever anymore. I reckon TDS and KH are the only measures worth monitoring in a tank...Any movement up and down, there's an issue in the tank that will show up as weak fish/fish diseases.......


----------



## sciencefiction (3 Dec 2018)

dw1305 said:


> Some "black-water" fish can only be maintained in soft acid water. This may relate to their inability to survive in environments with a high bacterial load, because the acidic, oligotrophic habitats have a very limited, and specialised, microbiota.



I think you're right on the spot, that certain fish are just not immune to a lot of micro-organisms that flourish in hard water, and it is where the problem comes from, and not the hardness of the water. But a trigger is needed first to further weaken the fish's immune system.....Improperly set up tank, be it lack of enough oxygenation, insufficient filtration, blocked filters, too small of a tank, too many fish, aggressive fish kept with peaceful fish, insufficient water changes, cheap food filled with fillers and no proper nutrition, too much food, too little food, etc...any of these factors will lead to fish diseases way faster than the hardness of one's water..
What we consider sensitive fish, are fish that are not naturally immune to common fish micro-organisms and bacteria and which are subjected to additional negative factors to further weaken their immune system. If the tank is not right, even in their ideal water the fish will still succumb to diseases...

I am not familiar with the physiological processes happening when a black-water fish is kept in hard water. I can only say from my own experience of keeping 3 types of black-water fish in my hard water that there are a lot more important factors to their well being than how hard the water is.....I'd say people may be finding excuses in the hardness of their water when they fail to keep fish alive....I know you're familiar with my fish arsenal but I keep clown loaches, kuhli loaches and harlequin rasboras...They don't show any ill effects and neither of them have fallen sick. Oldest are  6-7 years old now(clown loaches and kuhli loaches) and healthy. I hope they remain so for a long long time....However, it will not be my water that would kill them prematurely, but the lack of fresh water....or the lack of proper care on my part, or an accident of some sort.

I think one should keep the fish that inspire them to be a fish keeper, and take great care of them with clean water and suitable setup, whether soft of hard water...is not that relevant for majority of fish.


----------



## sciencefiction (3 Dec 2018)

Edvet said:


> There is discussion wether the 1 point drop will be correlated to the same CO2 level in harder and softer water.



It will not correlate to the same....Having hard water means you need a lot more [H+] to negate the existing  [OH-] normally present in high levels in harder water. Thus 1 point drop in hard water is a lot more CO2 injection than the same in soft water. However, if one's KH is low, regardless of whether the water is soft or hard(meaning GH), it will take a lot less CO2 injection to move the pH 1 point down. The main point is, all this doesn't matter as CO2 injection doesn't alter the properties of the water meaningful to fish. It is only dangerous on its own, as CO2 is toxic to fish...


----------



## zozo (3 Dec 2018)

sciencefiction said:


> Yes, because when you add soda bicarbonate, you only add [HCO3-] and [OH-], but not Ca2+ or Mg2+ , so dGH remains unchanged.



But even tho it is only measuring alkalinity it is expressed in °DH, thus it never the less is adding hardness.. And if there is nothing else in it, than this obviously is the Total Hardness.. As a trivia interpreting the GH as absolute Total Hardness no matter the elements than @Edward Shave  and his source is 100% correct with °DKH can never be greater than °DGH.

And since we have °e (°clark), °fH,°rH, °aH (in ppm) i can understand the general envi towards °DH writen completely in capital letters triggering a trivial discusion about "What °tf is what???" And so on the scientific world got completely fed up with this triviality and decided since 2007 lets make it world wide mmol/l and done with it!? 

Publicaly you can not change this drasticaly, it doesn't sell, only will result in enormous amount of °tf phone calls to the water company, since the majority is still old fashion generation.. Thus let them ponder a while longer with °DH to let them know what to expect from their coffee machines lifespan.

If the same question is asked 20 years from now all the kids will ask "What era are you from? Who is still using °DGH?..


----------



## sciencefiction (4 Dec 2018)

zozo said:


> But even tho it is only measuring alkalinity it is expressed in °DH, thus it never the less is adding hardness..



*CaCO3 + CO2 + H2O → 2 HCO3- + Ca2+
*
Well, the above reaction is adding both hardness and alkalinity


----------

