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The influence of water temperature on the health of your koi

As a koi keeper, you are naturally actively concerned with the living conditions of your koi. Koi are very sensitive fish. It is therefore important to keep a close eye on the water. Both the temperature and the chemical values of the water. It is advisable to measure the water temperature and the values of ammonia, nitrite, nitrate, KH, GH and phosphate at least once a month. You can read about the usefulness of measuring chemical water values in another blog, which will be published in 2023.

Water temperature

Water temperature is very important for koi. The koi reacts to the water temperature. For example, if the water gets colder than 8ºC, the feeding behaviour of the fish decreases significantly. Around 5ºC, the metabolism will have slowed down so much and the action of enzymes will have decreased so much that the food in intestines will no longer be digested. Eating food will then be counterproductive. Moreover, in nature, food is scarce in cold water. If koi were to continue actively searching for food, there would also be a risk that they would lose more energy by searching than they would gain through food. In winter, it is preferable to feed sinking feed rather than floating feed.

At what water temperature is it best to feed floating or sinking koi food?

The water temperature has a lot of influence on your koi’s metabolism. At a water temperature below 5ºC, the carp or koi will go into a kind of hibernation to save energy to survive the cold. In a temperate climate, in natural lakes, the lower water layers will not get colder than 4ºC. This is because water of this temperature has the highest density and is always heavier than water that is colder, or warmer. This is because warm water expands and ‘floats’ above 4ºC water, while water colder than 4ºC also floats upwards. This is because water below 4ºC starts to form ice crystals, which will rise above 4ºC water. Water at 4ºC is therefore the heaviest and is located in the lowest layer of water. Wild carp survive in this lower layer of water, so from an evolutionary point of view their bodies do not need to withstand water temperatures below 4ºC. In our ponds, due to a relatively small volume, water can cool down too much or even freeze. Our koi need to be protected from this. It is usually enough to cover the pond with a sheet. Some koi owners also choose to heat the pond. By the way, it is not true that koi necessarily die when temperatures are too low, but there is a chance. The cold depletes their bodies, or they literally freeze.

Protect the pond from too low a temperature

How quickly the water temperature cools or warms depends on the content of your pond. A large pond is less likely to fluctuate with air temperatures during the day or night, than a small pond. It is important that the minimum water temperature does not fall below the critical temperature of 4ºC in any case. This can generally already be achieved by covering the pond with a pond cover in winter. Another choice is to possibly heat the pond.

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Risk of disease in spring

In spring, the risk of fluctuating water temperatures is greatest, as koi are weakened during the winter months. Temperature fluctuations cause stress, and stress makes the koi more susceptible to parasites. When designing the pond, it is best to opt for the largest possible size and volume recommended depth is at least 1.5 metres and preferably 2 metres, to minimise fluctuations. Furthermore, a (large) part of the bacteria in your filter dies during the winter, which can cause ammonia and nitrite values to suddenly rise in the spring. This too causes stress to the koi. In case you don’t have a canopy or heated pond, we recommend keeping an eye on your koi as much as possible and when they start swimming again in spring, to have a health check. In addition, it is wise to add bacteria to the pond during the winter months and spring see bacteria blog.

Want to know more about koi health, pond construction and water quality management? Then contact Mark and send an email to info@carpcare.nl

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Do you have a question about one of our products, a general question about koi food or about keeping koi? With our many years of experience, we are happy to help you!

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