You can be sure of one thing in spring: rain. In the time period before Easter there can be rainfall of 40 to 60 litres per square metre. We would like to explain why this can become an acid test for your pond and possibly also a problem for your fish.
There are a lot of different minerals dissolved in your pond water. These are consumed by biological processes (e.g. nitrification) by your fish (e.g. mineral consumption), the plants (e.g. biogenic decalcification) and algae (mineral consumption). Frequent and heavy rain, which is softened pure water (KH = 0), leads to a dilution effect. This causes the KH in your pond to sink steadily.
A significant amount of the minerals responsible for the stability of the water can be measured with the carbonate hardness (KH). The KH stabilises the pH value and ensures that this is subject to only slight fluctuations.
Why is this important? The fish in the garden pond’s mucous membrane tolerates a pH value between 7.5 and 8.5. If this starts to fluctuate, and in extreme cases this can be by about 4.0 in 24 hours to over pH 10.0, the fish is exposed to stress and the mucous membranes can become severely irritated. You know this effect when biting into a lemon. To avoid these fluctuations and to protect the fish, a carbonate hardness of 4 ° dKH and higher has been proven to be good. With this value the pH level stabilises within the range mentioned above.
How to test the KH in your pond
With a simple colour change test you can determine the stability of your pond water in less than one minute. On the left of your colour chart you can see whether the carbonate hardness is available in sufficient amounts (blue colour indication) and on the right hand side you can interpret the measurement results you have obtained for the pH value, following the traffic light colour scheme of red/yellow/green. You don’t need to be a biologist or a chemist to do that!
So test your pond water every 2-3 weeks, every week in frequent rainfall, with the JBL PondCheck .
What to do, when the KH is lower than 4 °dKH?
Have you discovered that the carbonate hardness is lower than 4 °dKH or that the pH level is outside the normal range? Then you could carry out a big water change (min. 50%), but this is scarcely possible or affordable with a pond. It is quicker and more reliable to add the missing minerals by JBL StabiloPond Basis , especially to raise the KH and thus to stabilise the pH level again.
Can you also add JBL StabiloPond KH for this purpose? In principle this is possible. But we have modified the product specifically for use when pretreating the water the evening before an algae treatment, especially to raise the KH.