There are so many home lab sets for water tests... Which one to choose? They will set you back up to 50 quid but are these worth the price? We take a very careful look at the important water parameters and the testing procedures in the home labs produced by major manufacturers...
Let's have a look at the chapter on pH measurements for Koi owners
Despite all the abundance of information available on the internet, it is hard
to find matching evaluations of a healthy pH level suitable for kois. Only the
limits are given uniformly: from 6 to 9. Thus, the concentration of hydrogen
ions within this interval can vary up to 1000 times (since pH is a negative
decimal logarithm of their concentration). It appears there is as much practical
sense in this evaluation as in knowing that the Earth temperature may vary from
-50 to +50 degrees whence embarking on vacation to a different country.
However, simply evaluating the pH interval from 6 to 9 as harmless is completely
incorrect: it only shows in which environment fish can generally live in. Below
6 the bacteria die out and the nitrogen cycle breaks down, above 9 the interior
organs of fish are irreversibly damaged, starting with the kidneys. Within the
limits of this «safety interval» the acidity level of your water directly
influences another parameter – ammonia concentration, of which even the smallest
amount is proven toxic – hence the recommendations that diminish the interval of
According to JBL, the recommended pH value for a fish pond lies between 7.0 and
For measurement purposes two indicators and two scales are given: one from 6.0
and 7.6 and the other from 3 to 10. The first uses a unit of 0.2, the second
60 of my measurements spanning for 2 months indicated, with 100% assurance,
solely that the pH does not change: the solution kept the same color. This is
undoubtedly a positive result – fish take harsh changes in the levels of water
acidity quite badly – but an insufficient one. In my case, not a single sample
from the first scale, where they differ in brightness of blue color, was
appropriate, and the color saturation of the resulting solution was more
intensive than the end value of the scale. Using the second scale, the closest
were values of 7.5 – a circle of green color and 8 – the color of a marine wave,
otherwise known as ultramarine. It is hard to put the shades of color into words
(«sing me a rainbow» would not make a lot of sense) but the solution definitely
did match neither of the two, leaving me with no result at all: with these
values the pH concentration of ammonia differs up to three (!) times (see Table
SERA AQUA-TEXT BOX
In the SERA lab, «favourable values for pH in fresh water» are said to lie
between 6 and 8 and are measured with one indicator on a scale from 6.5 to 9,
with a unit of 0.5.
Here it was just as hard to evaluate the results derived from the measurements.
Once again, the saturation level of the resulted solution and the brightness of
sample colors did not quite match. The solution was paler and, failing to
reproduce brightness, corresponded to the values 8 and 8.5 which in fact
differed only in brightness of one and the same color. Or they did not
correspond to either of them. Frankly, such a «result» did not result in
anything but frustration.
The comparison conditions recommended by SERA («daylight, avoid direct contact
with sun») did not aid the procedure: the weak coloration of the solution did
not help matching the standards on rainy as well as on sunny days. It is worth
noting that a stand from the JBL kit shields the bottom part of the test tube
carrying the solution from excessive light and simplifies the comparison.
Do you want to see another picture? :) There is plenty on the site below.
Söll assesses the favourable environment for pond fish between the pH values of
7.5 and 8.5. pH measurements in this kit return the most precise results: a
measuring scale from 5.2 to 9.2 with a unit of 0.3 till 8.0 and with 0.2 for all
subsequent values. The kit has six different indicators for conducting the
reaction. Using each indicator the result will be determined either by a color
matching one of the three closest pH values, or by the fourth color that will
indicate the need to use a different indicator. After the reaction, one obtains
a solution of such a color that it is hard to mistake it for another result (for
instance 7.8 – pink; 8.0 – yellow). If you were to collect a water sample anew
and use an indicator suited for values higher or lower than the ones obtained,
the water will remain clear, which adds to the confidence that the achieved
result was assessed correctly. Performing such a check was sometimes necessary
since the standard color given in the manual represents a square with a side
length less than one centimeter and the pages of the manual are colored blue. To
determine the color of the resulting solution one has to find a white
background, checking against the standard at a distance – an unnecessary
complication of the procedure.
This is only a short fragment of the report, just to give you an idea of the contents. However, this is exactly what pH measurements are all about, right? There are many more parameters and many more observations on how well the products perform, with tables and illustrations. The full report is free of charge. For more information, please visit koilife.net/compare-test1
Thank you for your interest!