Page 78 - Koi Net - On-Line Koi Magazine - Issue 75
P. 78
WATER HARDNESS It’s really only the temporary hardness that concerns us
as Koi keepers. It is often referred to as carbonate
EXPLAINED! hardness or alkalinity (KH) and fish are able to directly
absorb the essential minerals that help make up this
temporary hardness. It also has the ability to buffer pH.
Doug Keen (The pH of water is a measure of how acid or alkaline the
South Hants Koi Club water is.) Koi can withstand a large range of pH values
IT’S VERY but they absolutely hate change! If the pH changes too
EASY TO GET quickly they become stressed.
It is often the case that some bacterial problems in Koi
CAUGHT OUT may initially have been caused by pH swings that
We often hear reference to the hardness of water
but what does this actually mean and how does this BY HAVING A caused the fish to become irritated and then damaging
affect our ponds and Koi? The following is an attempt themselves when they react to the irritation. The
to provide some answers whilst trying to be as KH THAT IS resulting wounds may develop into bacterial infections.
non-technical as possible! The below is also my TOO LOW **Therefore as KH buffers pH changes, it is a really great
understanding of how it all works, if anyone can asset to us Koi keepers.**
identify anything which is incorrect then I’m sure the
It is often said that the KH value for Koi should be
editor would be happy to print a correction.
100ppm or higher. Notice the value quoted was
Water has a magnetic like property and it will ‘collect’ expressed as ppm (parts per million).
as many impurities as it can. The purer the water the
Many test kits available to us originate from Germany
more power it has to ‘collect’. That is why RO water, and express the KH value as German Degrees of
THERE ARE which is a fairly pure water and used by some fish Hardness, but this is confusing as several countries
keepers, should only be run in suitable plastic pipe.
TWO TYPES Otherwise if, for example, copper pipe were to be used, including England and France have their own Degrees of
Hardness and each has a different value. Therefore
OF HARDNESS, it will strip off the internal surface layer of the pipe. The please always express KH in units of ppm (or mg/l which
water will then have an elevated copper content and
TEMPORARY eventually pipework leaks will be caused as the copper is the same thing), this is the correct Standard
International method. Please note I did not mention the
pipe would literally dissolve.
AND This ‘collection’ ability applies to all water and the war once!!!
PERMANENT water supplied by local water authorities will pick up It’s very easy to get caught out by having a KH that is
impurities such as calcium and magnesium deposits on too low, especially in early spring when winter rain has
diluted the pond water, also perhaps there have been
its long journey to our taps. Water with relatively high
less water changes by the keeper. Condensation
amounts of these deposits is called Hard Water* whilst
dripping back into the pond from pond covers tends to
water with relatively low amounts is called Soft Water.
be acidic and likewise rain is also often acidic. These
There are also two types of hardness, temporary factors combine and use up the buffer reserves of KH
and permanent. The permanent hardness is best and then the pH is able to swing, stressing the fish and
considered as the hardness that will not come out of at a time when they are particularly vulnerable.
the water without some type of process, for example by
Filtration too will lower KH. Filter bacteria absorb
applying a high level of heat or boiling. The limescale
hardness to ‘grow’ and in doing so convert it from
that you can see in your kettle is permanent hardness
Temporary Hardness (KH) into Permanent Hardness.
that has been removed from water in this way. The
Once KH has been ‘absorbed’ by them it will not be
temporary hardness is much easier to remove from the
released back into the water, even when the bacteria die.
water and for this reason it is considered temporary.
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