Posted by Janet Christian on January 07, 2006 at 11:07:25:
In Reply to: KH and GH levels posted byNancy on January 06, 2006 at 19:03:37:
Hi Nancy,
Neither the kH nor gH level should be a problem. kH and gH indicate the stability of the water -- e.g., the water's ability to maintain stable pH. Remember that most test kits are geared toward aquariums and tropical fish-keeping. You are much better off leaving those values alone than trying to artificially adjust them.
More fish die from attempts to chemically alter the pH, gH, or kH than from leaving the values at their natural point -- even if those natural points are high.
A little kH/gH 101 for those reading this who might not know:
GH measures the general hardness of pond water, particularly the hardness forming ions of calcium and magnesium. The GH should be medium to high in order to match the conditions that is preferred by the koi physiology.
KH is a German scale described as carbonate hardness. KH largely measures the soluble bicarbonate ions which have a very close relationship with the pH (acidity/alkalinity) of the water. kH acts as a buffer to maintain a stable pH. A medium to high KH shows that the pH is not likely to fluctuate and is therefore the most desirable.
Therefore, by measuring the KH, not only can you generally determine the pH of the water but also the stability of that p (i.e., Is that pH likely to change?).
If water has a high KH, then it will have an alkaline and stable pH, just what is ideal for koi. However, if the pH is acceptable, but the KH is low, then the pH will be unstable with a tendency to drop below the desirable alkaline levels. In this particular case, it would be possible to fall into a false sense of security if only the pH had been tested without testing for KH. This would have indicated a healthy pH but without the warning of it being likely to drop.
Water with a high KH is referred to as being well buffered, as it resists swings in pH.
Janet