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pH and KH explained

If you are new to the hobby.

Re: pH and KH explained

Postby firefly » Sun Oct 09, 2016 9:10 am

Mick wrote:The pH measurement of water is very simple to understand for experienced fish keepers but can be baffling to novices.The pH of water is determined by the ammount of free hydrogen ions in the water, the more free ions the more acidic the water. This is where the term pH was derived from (power of Hydrogen). Alkaline water will have a pH higher than 7.0, whereas acidic water will have a pH lower than 7.0
It is measured on a logarithmiic scale which means that the further the pH moves away from the neutral reading of 7.0 the greater the acidity or alkilinity increases per unit.
For example a pH of 6.0 is 10 times more acidic than 7.0 but a pH of 5.0 is actually 100 times more acidic than 7.0
Nitrates in the water can reduce the pH as they combine with the Hydrogen ions to form Nitric acid, another good reason for regular water changes. This is why the pH of tank water can drop just after a tank has cycled.

One of the most overlooked water parameters has to be the KH of the water, yet this is crucial to maintaining a stable pH in your tank.
KH (carbonate hardness) is the concentration of carbonate ions in the water. Carbonate ions will always try to attach to Hydrogen ions present in the water, the more that bond the higher the pH will be as the Hydrogen ions lose there power to acidify the water.
The by product of this process is carbonic acid whick breaks down into CO2 and disperses into the atmosphere. The KH of the water is the buffering capacity that it has with the pH
Using this knowledge any pH level can be created in the tank to suit your fish.
Sterile water from my RO unit has a KH of 0, the water from my HMA unit has a KH of 6. By mixing these two I can then raise or lower the pH to suit my needs.
The KH of the water should never be allowed to drop below 3 as this can cause a major pH crash.
KH should not be confused with GH (General Hardness)

With permission would anybody mind if i expanded on this a little? It is a good explanation please dont get me wrong, but i think it might be useful to give a slightly deeper explanation as it affects so many other parameters. I dont wish to offend, i guess its just the scientist within me :D.
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