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When do koi go dormant? | Decorative Ponds & Water Gardens Q & A

Q: When do koi go dormant?

Q: When do koi go dormant?

Helen – Minneapolis, MN

A: With winter officially starting in just one week, the cold weather is settling in across the country. Since your fish don’t have miniature submerged Koi calendars to check, what is it that tells your fish it is time to hibernate?

Koi are cold-blooded creatures, which means their body temperatures and activity levels are directly correlated with the ambient temperature. Koi are active and alert when their environment is warm and will start to slow down as the water temperature decreases. Once the water temperatures start to dip below 46°F your fish tend to stop eating and will retreat to the bottom of the pond. Your fish use the decrease in temperature along with the shortening day lengths as a trigger to prepare for winter.

As the water begins to cool, your fish will become less active as their bodily functions slow down. Less activity means a slower digestive process, less demand for food. It is this decrease in food digestion that warrants the use of wheat germ based foods like Pond Logic® Spring & Fall Fish Food. These types of food are easier to digest that regular food reducing the risk of leaving undigested food to rot inside a dormant fish, which can potentially be fatal.

As the temperatures continue to decline towards 40°F, the blood flow and respiratory rate of the fish will drop to an extremely low rate where their body is hardly functioning. You may hear people say that your Koi are sleeping in the winter and while fish do sleep this goes way beyond the standard drop in bodily functions associated with some much needed shut-eye. This extreme internal slow down ensure survival with even the most limited resources with cases of dormant fish lasting 150 days without food.

The whole over-wintering scenario sounds a little extreme to us but it is truly a natural and normal process for your fish. They do not require much attention in the winter but there are a few things you can do to ensure their winter break is a success. When a layer of ice begins to form over the pond, maintain an opening for gas exchange using an aeration kit or pond de-icer, like the PondAir™ & Thermo-Pond Combo.

Pond Talk: What do you do to help your fish through the winter season?

Vent Harmful Gases All Winter Long - Airmax® PondAir™ & Thermo-Pond 3.0 De-Icer Combo

We’ve had a mild winter so far, does this affect the dormancy of my fish? | Decorative Ponds & Water Gardens Q & A

We’ve had a mild winter so far, does this affect the dormancy of my fish?

We’ve had a mild winter so far, does this affect the dormancy of my fish? 

Ivy – Schaumburg, IL

We may be having a mild winter, but a mild winter for humans doesn’t really mean the same for your fish. During the winter months, fish living in outdoor ponds will go “dormant,” slowing down all their systems and responses in order to conserve energy during cold temperatures. Monitoring your pond’s temperature is easy – we recommend this handy Pond Logic® Floating Thermometer.

The signs your fish are ready for dormancy are relatively easy to pick out – colder temperatures will mean less food, to which your fish will react to naturally. Their metabolism and digestion will slow down, as will their movement in general, while they conserve energy. Don’t be alarmed if your fish appear “lazy” or don’t have any appetite – this is all normal. It’s also a good idea to wait until spring, or whenever it is consistently warm, to start feeding your fish again regularly. Do remember that your fish will require a couple days to digest their food and even if they become more active on a warm day you won’t want them returning to a dormant state while still digesting.

However, if Old Man Winter does sneak up on you, don’t wait until the first freeze to make sure your fish have enough oxygen and aeration to keep the water from freezing over. We recommend using these Pond Logic® PondAir™ Aeration Systems to keep your pond, and your fish, in good stable condition for the winter.

Some people like to leave their aeration system running year ‘round, so feel free to do so as well, we’re sure your fish won’t mind!

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