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 (Testing Water)
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I wrote the following articles for Koi Magazine.
Therefore they own the copyright but the Editor has given permission for them to be republished here.
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Testing Water Part 2
The second part of this article is a discussion of the methods of actually taking water tests and what the water parameters should be.
Part one of this article discussed the reasons for six important tests that should be regularly made in order to ensure that pond water is conducive to keeping koi in good health. They were ammonia, nitrite, nitrate, pH, KH (carbonate hardness) and oxygen. These six tests can be reduced to five if there is a plentiful supply of air. If it can be seen that there is a huge amount of air continuously going into the water, the oxygen test can be omitted. There is no need to test what is obvious each time you look at your pond. How often should these tests be done? For a new pond, these parameters cannot be tested too often, especially whilst the bio-filter is maturing and the pH is stabilising. Once a pattern of results has emerged showing that the parameters have stabilised at acceptable levels, a less time consuming regime can be adopted. Whilst the fish are active and feeding, making these five tests once per week will usually suffice. In an unheated pond in winter it would be perfectly acceptable if the parameters were checked every four weeks.
The frequency of testing may have to be varied according to location. Local conditions can dramatically alter the parameters of a pond. For example, most rainfall in the UK is slightly acid, but there are areas where koi keepers continually report problems with their pond water after heavy rain has washed air-borne pollution into their ponds. If your own experience shows that you are in a problem area and it is not possible to cover the pond to prevent this from happening, by all means increase the frequency of testing so that corrective action may be taken sooner rather than later.
To take a water sample from a pond may seem a simple enough exercise but there are a few points that should be borne in mind to ensure that the sample is representative of the water in the pond as a whole. Try to avoid areas such as near return inlets, waterfalls, or air stones. In a pond with shelves or gently sloping sides, avoid taking samples from very shallow areas. Water that is near the surface may already have begun to exchange gasses with the atmosphere and may have different characteristics to the rest of the pond, so take your sample from just below the surface. Keep a clean, small plastic bottle near the pond. Holding it upside down, push it into the water to a depth of about one foot. Turn it the correct way up and allow it to fill with water at this depth before bringing it to the surface. You will now have taken a sample large enough for all tests.
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Organise!
A typical ammonia test takes 20 minutes from when the reagents are first added, until the colour change will have completely developed and can be compared to the colour chart. A typical pH test shows a colour change immediately.
There is obvious scope here, to save time by starting the longest test first so that quicker tests can be completed during this developing time.
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Testing Methods
There are so many different test kits on the market that it is not possible to give much detail here as to how to use the various tests kits from different manufacturers. As usual, read the instructions and follow them carefully. There are however, a few points of general advice. Remember that as soon as the water sample has been taken from the pond, it will begin to interact with the air and it will begin to change. There is no need to rush but you should avoid unnecessary delays between taking the sample and beginning the tests. Do not leave the sample bottle in direct sunshine so that it has time to heat up and alter it's characteristics.
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Similarly, where a vial has to be left so that the reagents can fully develop, it is best to keep the cap on that vial and also shade it from direct sunshine. Where tablets are used, try to avoid touching them, especially with damp fingers, to avoid altering the test results by contaminating the tablet. Where "dropper" bottles are used to drop reagents into the sample, hold the bottle vertically or the droplets will not have the correct size/volume. Lastly, but most importantly, manufacturers of test kits will have done whatever is possible to make their kits safe, but some reagents are harmful, or even toxic.
Do not use your thumb as a cap for the vial if it needs to be shaken and if there are any safety warnings on the instruction leaflet, please feel free to read them and take notice of what they say.
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What should the ideal results be?
The most difficult parameter to understand is ammonia. A whole article could be devoted to this single subject. When koi excrete ammonia into their pond, it breaks into two forms, free ammonia and ionised ammonia. The proportion of each being dependent on pH and temperature, but it is only the free ammonia that is harmful. Scientists in the field of aquaculture have researched the effects of ammonia on fish and found that free ammonia levels below 0.02 mg/L were safe. Unfortunately, standard test kits cannot distinguish between free and ionised ammonia, they only measure total ammonia. Tables were produced where, by looking up your particular values of pH and temperature, the maximum safe value of total ammonia can be found. These tables are commonly reproduced, but they cover the full range of pH and temperatures that are found in ponds and aquaria of all types, not just koi ponds. This wider range means that there is less room for detail in the area needed by koi keepers. So, with due respect to the authors of these tables, I have gone back to the original research and re-calculated a new table that gives the maximum safe value for total ammonia in koi ponds and quarantine tanks, showing greater detail in this range. As with other tables, look up the pond pH on the left, and temperature at the top. The maximum allowable total ammonia is shown where they intersect.
Of course it must always be remembered that whilst the level of total ammonia, (the value indicated by a standard test kit), in a koi pond can never actually be zero as long as there are fish in it, the ideal value should be as near zero as possible and that values in this table are the maximum values that can exist on a long term basis without causing harm.
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Nitrite
Nitrite is easier to understand. The maximum safe level for koi is 0.2 mg/L and levels above this cause what is generally known as "Brown Blood Disease". The gills will look brown instead of ruby-red, and the fish will have difficulty "breathing". The haemoglobin in their blood will have changed into met-haemoglobin and will be unable to carry oxygen around their body. If either ammonia or nitrite levels are high, one way of reducing them is to stop feeding and make large water changes. This is not a solution to the problem; it will only temporarily reduce the severity of the effects. High levels of either or both of these are a symptom that the biofilter is not working correctly and this should be corrected without delay.
Nitrate
Nitrate does not have a standard allowable level because it is common in tap water and these levels vary considerably. The usual recommendation is that it should not exceed a level of 50 mg/L above the level in the domestic water supply. High nitrate levels, (especially when combined with phosphate from fish food), cause algae problems in ponds. Until recently, nitrate was not thought to have a serious effect on adult koi. New research is suggesting that although high nitrate levels may not cause serious health problems, koi may suffer from reduced growth or poor colour development if levels become high. Water changes, vegetable filters and modern filtration methods such as Bakki Showers will help to keep levels lower.
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pH and KH
pH and KH levels are probably best considered as two parts of the same parameter. Koi can adapt to any pH between 7.0 and 8.5, but they cannot do this immediately. If the pH changes over a long period they will be quite happy, but if it changes too quickly, they will be stressed. The pH should be kept within this range and also not be allowed to vary by more than 0.2 per day. pH can be adjusted by acids and alkalis, but if the dosage rate of these is inaccurate, it could easily change too rapidly or even go right out of the acceptable range entirely. Even if these acids and alkalis are added according to the correct dosage rate, this dosage cannot be accurately calculated without first measuring the KH. I always recommend that pH is adjusted by the addition of Sodium Bicarbonate. This has the advantage that if a dose rate of 100 gm/1,000 gallons is used, the pH will not change too quickly, nor can it ever be shifted outside the acceptable range.
Finally, do not consider regular water tests to be a chore, do your testing by the pond and use the waiting time as an opportunity to do another very important test – observe your fish.
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< Back to index Next article, Understanding Hanna >
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