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,
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.
