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Whats the importance of KH ?

Hi all,
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
 
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?

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
 
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,
 
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
 
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.
 
Hi all,
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.
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.
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
 
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.

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.


...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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