Using test kits in koi and garden ponds

Anybody contemplating whether to take the plunge or merely dip their toe into the world of koi would be well advised to carry out as much research on the many aspects of the hobby as possible before getting wet.

Koi keeping is an alluring hobby and quite understandably, we can soon get carried away with dreams of a perfect pond, filled with perfect koi all of which can be achieved at first attempt within budget and timescale.

It is through asking advice and speaking to koi dealers and keepers that we first start to appreciate how varied the challenges within the hobby can be and how multi-disciplined a koi keeper must be to achieve a perfect pond (if one exists!).

A successful koi keeper is first and foremost a fish lover, but also a biologist, plumber, linguist, civil engineer, mathematician and chemist……yes a chemist!

Chemistry and koi keeping?

When maintaining a koi pond we need to understand, analyse, interpret and respond to a handful of chemical data, sometimes on a daily basis. The water in which our koi live does not simply sustain their lives but will also undergo rapid chemical changes by interacting with all the other ‘players’ in its environment.

Where do we get our information on the chemistry of the pond water?

The more intimate we know the behaviour of our koi, the more reliably we can use our observations to gain a broad understanding of their state of health. As the health of our koi is largely dependent on the quality of their environment, we can soon gather useful information about the quality of our water simply by koi watching.

However, a more detailed analysis of pond water can only be determined by testing the water for a number of key parameters. This will not only give us more information than studying fish behaviour but will allow us to identify any problems and respond to them before they cause a change in koi behaviour.

Test Kits.

Test kits are the most popular method of analysing pond water. They rely on a chemical reaction between a reagent and pond water, resulting in a colour change that can be compared against a colour chart. Colourmetric test kits are available in 3 forms.

Liquid. A measured sample of water (usually 5 ml) is collected in a vial and test reagent added. A colour change will take place and after a set time, the resultant colour is compared to those on the chart and recorded. This is the method used to determine pH, ammonia, nitrite and nitrate whereas the number of drops of reagent it takes to change the solution from one colour to another is used to asses the various hardness values for the water.

Tablet. The water sample is collected in the same way but a tablet is added and dissolved in the test water to produce a colour change.

Test Strips. A cunning and rapid method of testing pond water for a number of different parameters. A single test strip, about the length of a cocktail stick will contain several different reactive pads, each one measuring a different parameter.

The strip is simply dipped into a sample of pond water and the colour of each pad compared to that on the colour chart.

Other analytical instruments can be used besides test kits to determine specific water quality parameters.

Thermometer – Liquid filled or digital

Refractometer – A simple method of determining the salt content of a koi pond.

Electronic Meters. Very accurate, if expensive, method of measuring pH, dissolved oxygen concentration and hardness.

When to test.

Pond water is tested to assess whether it is deviating from the desired limits required by koi. As the water quality is less stable and more likely to suffer from swings in quality then it stands to reason that a new pond should be tested more frequently than an established pond. This should also be the case if major work is carried out on the pond or filter and during the first few weeks of feeding in spring if your pond and koi have had a winter break.

Once the pond has maintained a stable chemistry for a good few weeks then testing water is not as essential and can be used to confirm that the hardness and nitrate levels are satisfactory, having a tendency to become a concern in mature ponds.

What parameters to test for.

It only makes sense to test your pond water if we know what we are looking for , and essentially, what to do if our vigilance has detected a problem.

1. pH. The pH of a pond can satisfactorily be found anywhere between 7 and 9. However, 8 to 8.5 is more desirable as it is less extreme and allows a slight deviation either way without the risk of affecting koi health.

If the pH is too high then it can be reduced by adding a chemical buffer (an acid) or by carrying out a partial water change with a source of less alkaline water. There are few natural causes of a high pH and if your testing reveals such a high pH then its cause should be identified and action taken to prevent it from reoccurring. A regular offender is new or untreated lime and cement work which can wash in to the pond.

If the pH is discovered to be too low, which may well occur naturally, then the remedy is quite straightforward. As fish and other organisms respire and give off carbon dioxide or bacteria break down ammonia then the natural by-products are acidic, causing the pH to drop gradually. This is acceptable as long as the pH does not fall too close to or below 7.0. A simple method of preventing the pH from falling is to add a source of limestone or calcium carbonate to the filter which will buffer the water. This is simply done by adding cockleshell or lime chippings in a net bag to the flow of water in the filter.

2. Ammonia is constantly excreted by koi and some bacteria through the breakdown of proteins. These organisms excrete ammonia because it is toxic and if it is not broken down in the filter it will accumulate in the pond water, making the whole pond toxic and irritable to koi.

An ammonia peak is more likely to occur in a new and immature filter system where the bacteria population responsible for its breakdown is not sufficiently great to break it down. If a positive reading occurs then feeding should be stopped and a partial water change carried out, with feeding only continuing once the ammonia level has returned to zero.

Nitrite. Ammonia is broken down into nitrite which is still toxic and has a nasty habit of being more persistent than ammonia, resisting being broken down. If a positive nitrite reading is experienced, the same action should be carried out as with an ammonia problem.

Nitrate is regarded as the ‘nitrogen bank’ where all nitrogen from ammonia and nitrite is eventually deposited. It is only harmful in excessive concentrations (>50ppm) and can be removed through plant growth (either a vegetable filter or blanketweed!) or through fortnightly/monthly partial water changes.

KH. This is a measure of the pond’s ability to resist swings in pH. The higher the KH, the greater the pond’s buffering capacity and the more stable the pH. The KH can be maintained at a satisfactory level by adding calcium carbonate compounds to the filter.

GH. A measure of the general hardness, which also has a loose relationship with pH and KH. As koi are hard water fish, a high GH should be maintained through similar methods used for pH and KH.

At first sight, the mention of water quality, chemistry and test kits may instil a real sense of fear and bring back memories of unexplained explosions of your childhood’s chemistry set. However, testing water and interpreting results will soon become second nature enabling you to take full control of your pond environment, benefiting from improved koi health and a greater sense of fulfilment from your pond.

Kill blanketweed and string algae.