The ammonia test
The wide range of allowable values for total ammonia made it impractical to test kits under all possible conditions so for the initial test a typical, non ideal, but common level of 0.3 mg/L was chosen.
The obvious problem when comparing the colour of a sample against a colour chart is that if it is not an exact match, and a degree of interpretation is required. With five out of the six kits tested it was easy to decide “slightly more green than 0.25” or “less green than 0.4” and in all these five cases, the kits gave satisfactory results in that they indicated that there was a low level ammonia problem.
The fifth kit did not perform well in this low level ammonia test. Despite repeated tests, and viewing the sample under different lighting conditions, the Waterlife kit consistently refused to show any colour change. At this low ammonia level it indicated “zero ammonia”. To be fair to the kit, it was designed to measure total ammonia levels up to 10 mg/L. Colour changes were slight up to 1 mg/L and more distinct in the range 1 – 10 mg/L so it was unsurprising that at 0.3 mg/L any colour change was too faint to see. The kit performed well in subsequent tests at higher ammonia levels.
Formed as an intermediate stage in the nitrogen cycle, nitrite is toxic to koi if the level is allowed to build up. The ideal value should be zero but in practise, true zero is rarely achievable, there is usually a low value that only an electronic photometer can detect.
Test nitrite test
The maximum acceptable level in a koi pond is 0.2 mg/L and so a 0.3 mg/L sample was prepared to see if the kits could show that the acceptable level of 0.2 mg/L had been exceeded. The kit with the lowest reading showed that the level was in excess of 0.2 mg/L. Three others said 0.25 mg/L and the JBL kit showed a perfect match for 0.3 mg/L. Therefore all five manual kits agree with the readings from both Hannas (0.3 mg/L). They all indicate that there is nitrite in the sample and they show that the level was between ‘just above 0.2 mg/L’ and ‘dead on 3.0 mg/L’.
Only three of the manufacturers supplied kits that tested for nitrate. It is generally regarded more of a nuisance that encourages blanket weed than a toxic pollutant. We usually try to keep the nitrate level as low as possible so a water sample with a nitrate content of 25 mg/L was chosen for this part of the test.
The nitrate test
The Waterlife kit indicated 0 mg/L. Again, being fair, this kit was intended to read up to 200 mg/L with the major colour changes occurring in the region of 50 – 200 mg/L. Blagdon showed the level to be slightly above 25 mg/L and JBL showed just above 20 mg/L.
Koi will adjust to any pH in the range 7.0 to 8.5 but do not let the wide range fool you into believing that it is an unimportant parameter. It is very important and should be checked regularly. The value must be stable and variations should not exceed 0.2. It should be checked at different times of the day to ensure that plant or algae respiration cycles are not causing daily pH variations due to fluctuating levels of dissolved CO2.
The pH test
For the initial test, a sample with a mid-range pH of 7.7 was chosen. There is little to say about this test, all kits produced the correct readings although I would have liked to see more individual colours on each colour chart range so that variations in excess of 0.2 could more easily be seen.
KH is another underestimated parameter. The key to a stable pH is to have sufficient carbonates (KH) in the water to buffer it against pH variations.
Some koi keepers try to emulate conditions in Japanese mud ponds by having a low KH. There is no reason why this cannot be successful. It is possible to have a very low KH and still have a stable pH but this should only be attempted by those with a commitment to water quality. For the average koi keeper who wants an easier life, and stable parameters, a KH of around 6°DH is preferable.
The KH test
Only JBL Labs provided a kit that tested KH. The method used is one called titration. This is where a reagent, (more correctly called a titrant), is dripped, one drop at a time into the sample until an abrupt colour change is seen. The drops are counted as they go in and the number of drops until the colour change occurs will directly give the value of KH in °DH. For example if it takes six drops before the colour abruptly changes, the KH is 6°DH. This is a very simple method that doesn’t rely on matching a sample colour against a chart, merely the ability to count drops and so it is unambiguous and accurate. The JBL kit gave accurate results.
The basic tests were intended to show whether manual test kits could correctly highlight that parameters were going outside accepted limits. Whilst these kits are never going to compete for accuracy with electronic photometers, all kits, except where noted above, performed satisfactorily. There is insufficient space here to give greater details but extended tests were also carried out with many more pond water samples with a much wider range of parameter values. All results were similar in accuracy to those described above.
(Click here to see the results)
Over the years I have found that, when matching the colour in a sample tube to one of those on a colour chart, women have better colour perception than men – sorry guys, it’s true! But that is mainly true for the occasional user, it can be outweighed by practise making perfect. The more often you use manual test kits, the more practiced you will become at judging what the various colours actually relate to in terms of parameter values. Lighting is very important. Precise lighting conditions depend on personal choice but a general rule that has stood the test of time is that diffused lighting is best. Outdoors, unless it is very overcast, stand in the shadows and face North. Indoors, a single light bulb or window will cause shadows. Where a colour darkens to indicate increasing levels, for instance, as in nitrate tests where a pale pink gets successively darker, shadows or light refraction at the edge of a sample tube may make the contents appear darker than they really are. Where possible, orient your position to eliminate shadows. Don’t compare the chart with the colour at the very edge of the tube; compare the true colour at the centre of the sample tube.
You read it here first!
A little known fact about ammonia test kits that show yellow for zero and go successively more green for increasing levels of ammonia is that they are based on a method where the first reagent used is a form of chlorine. This reacts with any ammonia in the sample to make chloramine. As other reagents are added, horribly complicated chemistry then goes on in the sample tube to measure how much chloramine was made and this is what ultimately causes the green colour.
Since dechlorinators remove chlorine, (obviously), I asked the manufacturers if they thought that dechlorinators added to the pond before a sample was taken might affect the accuracy of their results. Three replied that there was a possibility that dechlorinators or one particular dechlorinator additive could reduce the indicated ammonia level if excessive amounts were used or if a sample was taken too soon after the addition.
Without wishing to overstate this potential problem, it is a sensible precaution to ensure that only the correct amount of dechlorinator is added and that time should be allowed for it to thoroughly mix with the pond water before taking water samples. This is a point to consider at koi shows where frequent ammonia testing is done, often immediately after water changes with recently dechlorinated water.
Just for fun
To show that they have a sense of humour, chemists sometimes add little “chemist jokes” in their reports. In keeping with this tradition I have included a chemist’s joke in one of the pictures. The eagle-eyed among you might have spotted it. Make sure you get next month’s issue to see what it was.
[The answer was published in the following month’s issue - click here to see what it was]