# Whats the importance of KH ?



## tubamanandy (20 Jan 2014)

I'm fully aware of the importance of your KH level in a planted tank regarding stability/alkalinity but I don't know how important it is in the planted tank.

Is there an ideal level and why ?


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## Yo-han (20 Jan 2014)

tubamanandy said:


> I'm fully aware of the importance of your KH level in a planted tank regarding stability/alkalinity but I don't know how important it is in the planted tank.
> 
> Is there an ideal level and why ?


 
Although you say you are aware and tell us you aren't at the same time I assume the last is correct. It is important as a buffer for CO2. Some plants need it to be low (<4) but these only include specialized plants like Toninas, Eriocaulons. You don't want it to be zero though. That way your pH can drop very low and this does harm to bacteria and fish. On the other hand, I've seen perfectly healthy plants in KH=15, so anything between 1 and 15 (maybe even higher) is OK. Between 2 and 7-8 is preferred by most people.


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## tubamanandy (20 Jan 2014)

My wording was not the best, apologies. I guess I was really looking at a sensible KH to aim for in a planted aquaria


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## Aquadream (20 Jan 2014)

Actually I can demonstrate perfect plants at KH 0.
Just about any KH is sensible as long as the rest is there in plenty.
If any type of clay substrate is used in the tank the PH will never drop to a point of harming any live stock or plants.
In a quartz gravel based set up that's different matter. In such case minimum of 4 KH is recommended only to prevent sudden shifts in the PH. Other wise most plants and fish species are not that interested in the KH at all.


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## ceg4048 (21 Jan 2014)

Yeah, use whatever KH makes your life easiest, or most entertaining.

Cheers,


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## Marcel G (22 Jan 2014)

As Yo-han said, alkalinity (= mainly HCO3- and CO3--) acts as a buffer. This means that these ions neutralize any acid which shows up in your tank. So logically, if you have small amount of these guys in your tank, that they are able to neutralize only small amount of acids. BTW, acids are produced in each aquarium. So if you add a small amount of acid into your tank, these ions will neutralize it. BUT if you add more acid then these guys are able to neutralize, then your pH begin to drop ... VERY RAPIDLY! For each 1 piece of acid, 1 piece of alkalinity will deplete. As long as you have some alkalinity, your pH will not drop. But as soon as your alkalinity is depleted, your pH will drop. So it is advisable to have at lease some alkalinity, so that your tank can resist to acids, and to pH fluctuations.
By the way, 1°dKH (= 0,357 mmol/L HCO3-) is enough to neutralize 3 ml 31% HCl in 100L tank! So if you add 3 ml 31% HCl into 100L with alkalinity 1°dKH, your pH will not change, but all your alkalinity will be depleted (= your alkalinity will be 0°dKH). So if you then add a couple of drops of 31% HCl, your pH will immediatelly drop to 4-5!


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## darren636 (22 Jan 2014)

Ceg cracks me up. He's just so deadpan.


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## tubamanandy (22 Jan 2014)

So basically, the KH is really for stability against PH drop and the plants are not really that bothered what the KH is.

Reason I asked is that many of my older plant books advocate keeping KH at around 5 for the plants - I guess this is simply now old information.


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## Marcel G (22 Jan 2014)

Yes, I don't know any reason (although there may be some) why plants would need HCO3- and/or CO3--, except for plants that use carbon exclusively from (bi)carbonates.


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## ceg4048 (22 Jan 2014)

There are no plants that use bicarbonate or carbonate exclusively. Bicarbonate use by plants is an act of desperation. It's a very expensive in terms of energy requirement.

Also, not only are the vast majority of plants not bothered by what the KH value is, but they also don't care what the pH is, and neither are the fish concerned.

Cheers,


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## ivydree (30 Jan 2014)

ceg4048 said:


> and neither are the fish concerned.


 
So you're sayiong that all that's all over the internet regarding KH and pH for fish is rubbish?


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## ceg4048 (30 Jan 2014)

ivydree said:


> So you're sayiong that all that's all over the internet regarding KH and pH for fish is rubbish?


Yes. Popularity of an idea can never imply validity. Truth is never democratic.

Cheers,


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## ivydree (30 Jan 2014)

ceg4048 said:


> Yes. Popularity of an idea can never imply validity. Truth is never democratic.
> 
> Cheers,


 
I have to agree with you, not saying that majority is always right. But then again, how comes all you can read everywhere says, you have to have soft water for this and this fidh and hard water for this one... I'm confused....

So tipically all thread like: love rams ,hmmm hard water | UK Aquatic Plant Society are useless?!


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## ceg4048 (30 Jan 2014)

Well, you know that most of the common fish and plants come from soft water zones such as the Amazon system or the Congo River Basin. On the other side of the coin there are the hard water Rift Valley species. People automatically assume therefore that if a plant or fish is found in a specific region, then the water parameters of that region must be duplicated in order for that fish or plant to survive. While this is sometimes the case form many plants and animals, it's not always the case. It can easily be, and often is the case, that the plants and fish are simply playing the hand they were dealt and have  adapted to those conditions. It does not automatically mean that those conditions are perfect for them, only that they have figured out a way to deal with the shortcomings of their environment. When moved to a different environment they adapt to the new conditions with little fuss, especially if the new conditions are more favorable to growth.

When I observe aquatic plants in their natural habitat, their condition and appearance is a far cry from what we would call ideal. They are often tattered and weary looking. The so-called "Nature Aquarium" verdant and healthy appearance is an illusion. Plants rarely look like what we see in healthy Amano type scapes.

This is not to say that all parameters can be ignored in every case. I always have better luck breeding soft water chiclids when the water's hardness is constrained to the lower limits than when it is allowed to be as hard as possible, but there is never an issue with basic health or longevity of the fish even when the hardness and/or alkalinity is allowed to hover in the extreme high end. Discus are sometimes even bred in hard tap water many times. We definitely have plenty of empirical evidence that plants from soft, nutrient poor waters do brilliantly in hard, high nutrient water. We see that every day. Of the 300-400 plant species available to us, there are only a handful of plants that have shown to do much better at the softer end of the scale. I've deliberately added GH Booster to my already hard tap water to see what the differences were in growth and health performance and they just carry on. Others here have reported similar experiences, so it isn't a fluke.

The one parameter that people never talk about, which turns out to be the most important when it comes to plant and fish health is the cleanliness of the water. Cleanliness in the sense of low organic pollution. The plants and fish come from areas of pristine conditions, free of organic waste buildup and high in Oxygen. If you simply keep the tank clean and free of organic debris then all those other parameters that folks obsess over are rendered moot. If there is a secret to plant and fish keeping is that of cleanliness via water changes and removal of organic debris. CO2 injected tank are notorious producers of organic pollution due to the byproducts of plant metabolism. Their debris will clog the filter and settle into the sediment building up to toxic levels. I'm very particular about cleaning and so I don't have fish/plant health problems and my tanks don't get algae. It's really very simple, but the same folks who preach about the importance of KH or pH are the same who refuse to do large water changes or to keep their tanks clean in the misguided effort to maintain those parameters.

In that thread you linked to, look at posts #7 and #9. A breeder spawning his rams in TDS 660, and a hobbyist having kept wild specimens at 850. That is super high. So the other poster's failure may have nothing to do with the water hardness at all.

If you check the very top center of this photo, you'll just be able to make out a Ram guarding eggs which are inside the grove of L. aromatica. This is also a 850 microsiemen tank with KH 15 and GH 25+.





Cheers,


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## ivydree (30 Jan 2014)

ceg4048, you just changed my life!
Thanks for explaining this so clearly.

I'm a new person now! (best hopefully...)

BTW, sorry for hacking the thread in the first place...


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## Ravenswing (30 Jan 2014)

ceg4048 said:


> The one parameter that people never talk about, which turns out to be the most important when it comes to plant and fish health is the cleanliness of the water. Cleanliness in the sense of low organic pollution.


 
+1! At the same time we argue if its OK or not to keep Cherry barbs at pH 7,5 when The Book says max 7,0, the waterquality (in terms of BOD) of the tank is totally ignored. Im sad to see how often people are offended when they are told to have dirty tank, wich is the case. Im sad to see how often we focus on "right" water parameters instead of focusing the cleannes of the water. We worry wrong things! Does worrying about pH, KH or PO4 make us better fish keepers? Im afraid of.



ivydree said:


> So you're sayiong that all that's all over the internet regarding KH and pH for fish is rubbish?


 
Well...I think we have learned a lot of new things about mechanisms and reactions in aquarium chemistry in a short time (and thats thanks to people like Darren, Clive, Tom Barr.etc etc who brings us all that information). Earlier we just observed The pH, is it bad or good, but nowadays we know it is something that tells us something is happening in the tank. Its our job to think what is happening and why and then, but just then, we know if its good or bad. We have started to learn that test resuts are just numbers and we have to understand what they mean, otherwise we are lost. We have also learned that aquarium is* not* the same as rivers or lakes no matter how much we try to create such "natural" (?) enviroment to our fish.


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## ivydree (30 Jan 2014)

You guys made me curious. Here's an interesting reading about water parameters.
Haven't digested it all but still, I found it pretty interesting especially the part where it says that water "hardness" or "softness" is actually measured by GH and not KH... Oh well... need to learn more I guesss.....

Here's the link: The Effect of pH (and not only) on Fish=

I'm still very noob I realise.


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## tubamanandy (30 Jan 2014)

I think the old adage of `the solution to pollution is dilution` is so true when keeping plants - water changes


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## ceg4048 (30 Jan 2014)

Thanks for the link. The article provides comprehensive coverage of the three most popular obsessive parameters, pH, KH and GH. Unfortunately the information provided is completely irrelevant.

In Central and South American freshwater systems there are no buffers in the waters and tannic acids leach from the fallen leaves on land due to heavy rainfall. The tannic acids are byproducts of the natural insecticides that the trees use to protect themselves from leaf browsers such as insects and mammals.  These acids leach into the streams, often staining the water a tea color.




Fish move from one stream to another where the amount of tannic acid varies. When it rains the waters get diluted and then as the runoff from the land enters the stream or pond the acid concentration changes. Fish and plants are constantly facing changes in pH in the water. Their bodies are easily able to cope with this. The reason is subtle, and it has to do with the _kind_ of acid that is dissolved in the water. There are two fundamental kinds of acids. Weak acids, which do NOT disassociate very much and which therefore do not appreciably change the total quantity of Hydrogen ions, and the other is Strong acids, which disassociate almost completely and which floods the environment with massive amounts of Hydrogen ions.

The example I always like to use to describe the difference is that of Vinegar versus battery acid. Both are acids and both produce H+ ions. You would not think twice to pour vinegar on your fish & chips, but I think you would hesitate to put battery acid on those same fish & chips, right?

Vinegar is a very weak acid. It's so weak that it only produces a very small amount of H+.  That small amount of H+, although fairly innocuous, still has an effect on the pH calculation, so of course when you eat vinegar the pH in your mouth will fall rapidly. Is it harmful? Of course not. Well, this is the same story with tannic acids, CO2, and all the other things in the tank water that have an effect on pH.

On the other hand, if you were to put Muriatic acid in your mouth, you probably would be without a mouth for the rest of your life. Muriatic acid, used in batteries and pools is a killer because it releases massive amounts of H+ which, in such large volumes, electrically attack almost any material it touches. The pH falls but it is not the pH calculation that is doing the damage. It is the H+. It just so happens that the way in which the calculation is performed, the pH number itself will be similar as if vinegar was used.

So when the author makes the statement,


> *The fish* were accustomed to a certain H+ concentration. Then, suddenly, they are facing new water coming in their tank, which only contains one hundredth of the normal H+. This is a shock by itself, a very serious shock. While in stress, the fish try to adapt to the new situation when suddenly something is added in the water which creates a new solution with 100 times more H+. No organism can adapt to this sort of fluctuations!!


he is completely ignoring the difference in the types of acids. The fish & chips example already gives you proof that organic tissue (and one of the more sensitive tissues, mouth and tongue, is not affected adversely by the presence of weak acids or the large pH drop caused by weak acids.. It is very similar case for fish. Tannic acids, CO2 and a host of other organic acids being produced in the tank do not affect the fishes tissues, who combat the chemical agents in the water by secretion of a mucous slime coating, for example. Fish are not affected by pH changes large or small. What they are affected by is the presence of toxic substances which does damage their tissues. What's ironic is the acid buffers many people use, like "pH Down" type products, are toxic acids, which harms fish, specifically because the active ingredient is a strong acid.

Another area where the author completely ignores important facts is that there are no test kits that actually measure KH. KH test kits are incapable of directly measuring the concentration of Carbonate or Bicarbonate ions. The fact is that there are many different ions that behave like carbonate/bicarbonate, and so the kit is capable of telling you what the resistance to pH change is in the water as a result of the concentration of unidentified anions, which may or may not be carbonate/bicarbonate. This may seem a trivial point, but it's actually very important. The chemical behavior of carbonate/bicarbonate is not only limited to it effect on sequestering H+, but a host of other chemical characteristics and interactions (it's relationship to carbonic acids equilibrium, for example) These characteristics may have some effect on fish, but they will be different effects than all the other anions in the water that have an effect on alkalinity, and which also may be totally irrelevant to fish.

This statement is also absurd:


> Again, an instant raising of the GH from 10 to 20 will cause too much stress to your fish. The living cell has a certain osmotic pressure in the interior (proportional to the concentration of particles in the cytoplasm) and has reached a dynamic equilibrium with the surrounding osmotic pressure.


GH, the concentration of Calcium and Magnesium ions, has no osmotic effect. Bicarbonate does, but NOT Ca/Mg, but the author just feels free to lump them together and he uses arbitrary value to determine what is a safe change. Fish ignore GH changes. They do not care. I do this all the time without any effect on short term or long term health. Where did they get these numbers?

So, according to the logic, it's OK to add buffers, which have an immediate impact on raising the KH, but it's not OK to suddenly raise the GH? That makes no sense.

Here is more myth. The article becomes more sensationalist as it goes on:


> *Thus*, people aiming at a very low KH with a carbon dioxide injection should be very careful because in reality they are always at a razor's edge. If something goes wrong, there is nothing to stop their pH from plummeting or sky rocketing. There are many factors which can have such an effect. The wrong type of stones and rocks, a sandy substrate full of calcium compounds, a dead decaying fish, dying plants and many more.


Again, tested this theory time and time again and it's complete hogwash. Here is a sample of what happens plants and fish in low KH water and when the pH "plummeted" from 7 to about 3 with daily injection of CO2:










Furthermore, we should know by now that this statement is not really true either:


> *The* formula which links Carbon dioxide, carbonate hardness and pH is a very useful one and allows you to predict what the final conditions will be. It will directly show you how much carbon dioxide is dissolved in the water so you can increase or decrease the amount injected to get optimum CO2 levels.


We know that other acids in the water affect the pH in such a way as to disrupt the CO2 calculation.

At least the authors recommend against the use of alkaline or acid buffers at the end of the article but there is a lot missing and it appears to be regurgitation of a lot of misinformation without actual experimentation.

Cheers,


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## Rob P (31 Jan 2014)

Brilliant Clive!!!


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## dw1305 (31 Jan 2014)

Hi all, 





ceg4048 said:


> The article provides comprehensive coverage of the three most popular obsessive parameters, pH, KH and GH. Unfortunately the information provided is completely irrelevant.


 I'd have to agree with Clive, it is an article that contains a lot of "facts" some true, some not, but all of them irrelevant, or only tangentially relevant, to the issue.

The problem has a lot to do with the pH scale, which is a ratio. Because it is a ratio it doesn't tell us anything useful about amounts.

At pH7 we have equal amounts of acids (H+ ion donors) and bases (H+ ion acceptors) in solution, but we don't know what that amount is, it could be 1:1, 100:100 or 100,000:100,000,  pH doesn't change, as long as acids and bases are in balance.

If you keep fish from salt rich, buffered alkaline water (Lake Tanganyika etc) small changes in pH reflect large changes in water chemistry. If we start with very hard carbonate buffered we have a huge surplus of bases and we need to add an equally huge amount of H+ ions to reduce the pH. If we keep fish in very soft water any small change in water chemistry, in the amount of acids or bases, has a large effect on the acid:base ratio, and changes the pH. The pH can't be stable. 

In this scenario I've added a very small amount of very weak acid (like H2CO3) to be in our heavily buffered water neutral water. We now have a ratio of 100,001:100,000 (H+ donor:H+ acceptor) and no change in pH, in our lightly buffered water we have a ratio of 101:100, and very little (if any) change in pH, but in our very soft water we now have 2:1 acid:base and our pH "crashes".

Does this pH crash kill your fish? No it doesn't. How do we know? because it is what CO2 users do every day when they turn the CO2 on. When they turn the CO2 off, CO2 levels equilibrate with atmospheric levels, and pH returns, just as rapidly, to its initial value.

cheers Darrel


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## Ravenswing (1 Feb 2014)

Hi!

Very informative thread indeed! Thank you Clive and Darren clearing this whole thing to us!

I have couple of questions just for figure this out to myself:

1) Is big amount of H+ ions problem just because of the *big* *amount* of plus charged ions? Or... Is the problem caused just because of the *nature of positive charges *as we know them quite troubled and busy? My best bet is...both? No? Something else? How about the H, does it has some role in the puzzle?



ceg4048 said:


> GH, the concentration of Calcium and Magnesium ions, has no osmotic effect. Bicarbonate does but NOT Ca/Mg,


Could this be explained a bit please since I have always thought that all (well not maybe all but...) ions have effect on osmotic pressure and mechanisms? Btw, Id love to hear more about fish osmotic system and how does the fish handle salts etc, I have found very little information  about this.

Maria


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## ceg4048 (1 Feb 2014)

Ravenswing said:


> 1) Is big amount of H+ ions problem just because of the big amount of plus charged ions?


Yes, That is why acids are used in batteries. The effect of strong positive charge due to high number of protons is that it attracts and transports large number of negatively charged electrons across a barrier. Strong acids are toxic because their high density H+ rips electrons from their orbits in the fishes tissue, instantly damaging the tissue. With weak acids the quantity is much smaller and there is enough resistance by the tissue molecules  to hold on to their electrons.


Osmosis occurs with any solute in any solvent, but the mechanism and the affect each ion has on tissues is different. Ca++ has an indirect effect in osmoregulation primarily because of it's action of affect the presence of Na+ and Cl-.
Osmotic pressure as it affects tissues is causes primarily by Na+ and Cl- which are strong ions whose presence in the cell alters the cell volume.

Ca++ and Mg++ are used in other useful function such as enzymes, but Ca++ does act to control the behavior and movement of K+, Na+ and Cl+. In fact, the fish is always trying to accumulate Ca++ and Mg++ ions because in the soft Amazonian waters, these ions are not readily available. The fish has to eat food, hopefully containing these metals which are in short supply in native waters.

There really are 3 basic osmoregulatory functions the fish has to deal with.
Control of Tissue osmotic pressure
Osmotic composition of the body fluids (ion composition)
Nitrogen excretion

Freshwater fish are at risk of drowning because the concentration of ions in their bodies is higher than the surrounding native waters. That also means that the _concentration of water_ in their bodies is lower than the surrounding waters. That means water diffuses into their bodies and so fish have to almost constantly urinate in order to pump all the extra water out of their bodies. The penalty they pay is that because of the continual urination, body salts also escape with the water. In nutrient rich water the problems associated with mineral loss due to urination is actually lessened.

The job of excretion is the kidneys which filter out excess ions and sends them out, if necessary, via feces.

The outer skin layers of the fish, which has good permeability, which allows for gas exchange, nutrient uptake and so forth, also results in water ingress and ion loss. To combat this some produce and deploy into the cells a type of protein called aquaporins.  Aquaporins facilitate rapid, highly selective water transport which allowins the cell to regulate its volume and it's internal osmotic pressure according to hydrostatic and/or osmotic pressure differences across the cell membrane. 
So it's very easy for these fish to deal with excess ions, and that's why soft water fish adapt so easily to hard water.

Now, again osmotic composition is only one of the factors associated with living in hard water. Chemical compounds and ions have multiple and different effects, so that's really only a slice of information. Osmoregulation, alone, is not a problem for these particular fish as it relates to Ca++ and Mg++. Conductivity, alkalinity and so forth are different issues. So some things are positive and other things may be negative. Ion composition is also not really a problem as there are different mechanisms for controlling  them such as dedicated ion transporters , the kidneys and the gill tissues which are specifically designed to have an array of selective transporters.

Therefore, in hard water, depending on the composition of that particular tap there can be ions which have a disruptive effect, such as Sodium (Na+) Potassium (K+) and Chloride (Cl-) but many of the other components are much less of an issue or may even have a positive effect on the activity of the disruptive components.

Cheers,


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## zanguli-ya-zamba (1 Feb 2014)

Hi Clive, I can see that you have not forget that acids batterie story. Haha


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## Ravenswing (2 Feb 2014)

Hi Clive and thank you very much for your answer, it helped a lot!

Cheers, Maria


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## Ravenswing (2 Feb 2014)

Yahoo, shes thinking ff (fastforward) again...Ok, now we understand excatly why H+ ions are harmful, but how about OH- ions? Do they have some effect on fish or water chemistry? My tapwater is pretty alkaline (pH8) and never thought it as a problem but is it unproblematic just because of minus charged ions and their "peaceful" nature?  How about pH...for example...12 water (if such water exists...), if its harmfull, why? I ask this beacause we can read so often that is soooo harmfull to keep fish pH8 or 9 water thou we can also read that many hobbyists keep (sof water) fish alkaline waters without problems. But if, if water is even more alkaline than that, what will happen in fishs physiology?

Yesyes, it this age of asking things...Iv just found how interesting chemistry actually is!

Maria


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## roadmaster (2 Feb 2014)

I'm still struggling with the notion(Is all it is to me) ,that softwater species will readily adapt to hard alkaline water,live just as long,just as comfortably.
Same applies to fishes that thrive in hard alkaline water's such as the  Tanganikian's when kept in soft acidic water's.
I can add peat,R/Owater, and mix it  with my 12dgh tapwater and keep, and breed some the softwater species fairly well, but without doing so ,,I and perhap's hundred's of other folk's  struggle.
And don't presume to suggest that it is cause my water is dirty for this is not so in my case.(have raised domestic Discus from babies in this water).
I have kept and manged to get free swimming fry from the German blue Ram's,appisto's, many of the tetra species, by cutting my tapwater sometimes by 50%. But without doing so ,the fishes seldom produce fry and maybe 1/2 of those purchased manage to live more than a few week's,perhap's month's.
I have alway's thought it was the hardness of my water that had negative effect on those softwater species I have kept over the year's for thing's went much better from longevity standpoint when my water was cut with R/O.Peat.


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## dw1305 (2 Feb 2014)

Hi all,





roadmaster said:


> I have alway's thought it was the hardness of my water that had negative effect on those soft water species I have kept over the year's for thing's went much better from longevity standpoint when my water was cut with R/O.Peat.


I think you are right, in my experience "black water" fish are definitely short-lived and unhappy in harder water. 





roadmaster said:


> Same applies to fishes that thrive in hard alkaline water's such as the Tanganikian's when kept in soft acidic water's.


 I think they are even less happy in soft water than soft water fish are in hard water. 





Ravenswing said:


> Ok, now we understand excatly why H+ ions are harmful, but how about OH- ions? Do they have some effect on fish or water chemistry?


 Pretty much, strong bases have an excess of O-H ions and are "caustic",  in that they cause chemical skin burns which if you are fish is going to wipe your gills out etc. You can neutralize a strong base with equal volumes of a strong acid, and you end up with a non-corrosive neutral solution (in theory, in practice you end up with skin burns from both acid and base).

In the same way that there are fish adapted to acidic peat swamps with very low pH, there are a few cichlids that can live in very alkaline water <Lake Natron - Wikipedia, the free encyclopedia>.

cheers Darrel


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## ceg4048 (2 Feb 2014)

roadmaster said:


> I'm still struggling with the notion(Is all it is to me) ,that softwater species will readily adapt to hard alkaline water,live just as long,just as comfortably.


Well, I've not had any health/longevity problems at all with the fish that have been in my hard water tanks. I have had Rams going through the motion of breeding but never produced any wrigglers. Had eggs, but yes, it's easier with softer water. Even so, dwarf chiclids are not the only soft water fish and they may be a bit special. What about all the other species like tetras and characins? They come from exactlyu the same waters and there doesn't see to be any issues keeping those fish healthy. The same can be said for the Congo river species. Kribs breed like rabbits in any water, yet they hail from soft waters.



roadmaster said:


> Same applies to fishes that thrive in hard alkaline water's such as the Tanganikian's when kept in soft acidic water's.


I don't have much data on this one so I don't know for sure. I do know that freshwater fish in temperate zones don't adapt well when hard components are added to the water. For Rift valley fishes, if the concentration of water in their tissues is higher than the concentration of water in the surroundings then they become dehydrated and have to drink water constantly. The same applies to marine fish as regards the Na+ concentration. They have to constantly drink. Rift valley fish kept in soft water risk ion loss in the tissues but wouldn't have to drink as much water. I'm sure there is a range of possibilities depending on how soft the water is, what their diet is and so forth. Marine fish don't stand a chance in freshwater.

As I mentioned, breeding is a different story because it's triggered by stimuli that may not be as easily achieved in hard water. Whether that has to do with conductivity, or some other phenomenon, I'm not sure. But we know that discus come from the same waters as Apistos and that there are many Discus breeders who use hard water, so I don't see why this is such an unbelievable possibility.




Ravenswing said:


> ...Ok, now we understand excatly why H+ ions are harmful, but how about OH- ions? Do they have some effect on fish or water chemistry?


Yes, OH- is a reducing agent as powerful as H+ is as an oxidizing agent.  A compound which disassociates to produce an  increase in the concentrations of OH- is called a Base.When there are large numbers of OH- they will easily give up their electrons in chemical reactions and change the composition of the materials that they are in contact with as a result.

However, it is exactly the same story with OH- as it is with H+: The pH alone tells you nothing about the actual quantities of OH- released into the water. Only that there was some ratio change. So as before, it depends on why pH rose. Was it due to a weak base, or due to a strong base? An example of a strong base is Drain Cleaner/Oven Cleaner, commonly known as Lye. This material is Sodium Hydroxide (NaOH) and disassociates into Na+ and OH- almost totally, producing massive increase in the OH- concentration.

Ammonia (NH3) and Ammonium  (NH4+) are considered weak bases because when they combine with water the net effect of the reaction is a slight increase in OH- concentration but not a whole lot. Even tho it is a weak base, NH3 is extremely toxic, even though it is a weak base, but it's toxicity lies in the structure and effect that NH3 itself has on tissue. It's toxicity is not related to the OH- concentration level.

Cheers,


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## Ravenswing (3 Feb 2014)

Thanks Darren and Clive once again for figuring this pH-thing out. Thanks to you, first time I feel I understand how it works and its meaning in aquarium. Hope this has helped other hobbyists as well!


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