Do Koi Fish Hibernate? 4 Facts You Must Know

Do koi fish hibernate?Do koi fish hibernate? We all know that koi fish tend to thrive in a natural environment, which is why they need outdoor or indoor ponds.

But what happens when the pond freezes over and your koi fish are left there? Will they also freeze? Or do they have some sort of mechanism that will help them cope in that situation?

Koi fish hibernate during the winter. However, it is not the same as other animals where they will stock up on food and be on an endless slumber. They will stay at the bottom of the pond while floating upright. Their metabolism and heart also slow down when they go into hibernation mode. 

This does not necessarily mean that you must leave your koi fish in the pond in extremely cold temperatures. A perfect example is when you know for sure that the pond will freeze. They are still not perfectly equipped to survive given this situation.

If you are curious to know what you can do to your hibernating koi fish, this is the right article for you! We are going to talk about what happens to them during their hibernation as well as how you can ensure that all of them are healthy. So keep on reading for more information!

Do Koi Fish Hibernate?

As we have mentioned earlier, koi fish go into hibernation, but it is not the same as the hibernation of other animals, such as bears. They actually go in a state of torpor. So, what is torpor? It is just a fancy way of saying hibernation that is of short duration.

Being in a state of torpor will help the koi fish conserve their energy that will be used in high energy activities on the contrary.

It is also good to note that it is a bit difficult for your koi fish to snap out of this state. This is not something that they can do abruptly, instead, they need to ease themselves out of it slowly but gracefully.

You might think that koi fish will benefit from this cold period since they are cold-water fish which means that they are not tropical, but the truth is, extended periods of cold and dark spells are still not good for them.

In fact, their immune system can be damaged and may even completely shut down.

With that said, if ever you are planning to have koi fish which will be in an outdoor pond, you really have to be informed in all the ways you can support them when they go into hibernation mode (we show you what you should do later in this article).

In this case, you can simulate their natural environment but at the same time, provide them with a situation that will also be beneficial to them.

What Happens When Koi Fish Hibernate?

Let us now take a look at what happens at the bottom of their pond when your koi fish go into hibernation mode. Surely, they are not just sleeping, right?

1. Position

It is truly a wonder how they manage to stay upright when they just “sit” at the bottom of the pond. They maintain this position by tucking their pectoral fins under their bodies.

Keep in mind that the pectoral fins are the ones that are in charge of movements like side to side and up and down.

Therefore, when they are tucked away, this ensures that your koi fish will remain upright and almost “still.” We use the term “still” because they still manage to float and sometimes they will slowly move from one point to another without using their pectoral fins.

2. Behavior

It is a common misunderstanding that your koi fish are braving the cold temperature. In fact, they are staying at the bottom of the pond as the water there is warmer. The opposite thing happens when it is the warmer months, the water at the bottom will be colder.

It is really interesting to see that sometimes, your koi fish will line up during hibernation. In fact, they will also be evenly spaced and they will face the same direction.

You might think that they are doing this so they can share body heat but since koi fish are poikilothermic (meaning, cold-blooded fish) this is not the case.

The truth is, they are just trying to take up space where there is warm water. Therefore, if you house them in a larger pond, they will have a random formation. The same thing goes in terms of the directions they are facing.

As for their activity, it will always be based on the state of the temperature. When the temperature of the water is between 45 F to 55 F they will still slowly go around the pond. They will also sun themselves when the conditions are well, specifically if the pond is still not forming any ice.

It is only when the temperature goes below 45 F that they will remain still. The same goes for instances where the sun is still out. During this time, they should not be fed but this does not necessarily mean that there is no form of sustenance for them.

In fact, they will somehow scrape the sides of the pond to ingest some algae that are nutritious. Usually, these are found on the rocks at the bottom of the bond or at the sides of the pond. In this way, they can store more energy and get some calories.

3. Metabolism

In the wild, koi fish will naturally slow down their metabolic process as it is extremely hard to find food during the winter. The same happens even though they were bred in captivity and they have an abundance of food.

This is also the reason why you should not feed them when the temperature in the pond drops to 51 F.

In the event that you try feeding them, they will refuse to eat as they are preparing to go into hibernation mode. They will not only slow down their metabolism but they will also try to not to move around so much so as to preserve energy.

They will move from time to time, but they will not use their pectoral fins. Their movement is just enough so that their joints will not freeze while they are trying to remain still at the bottom of the pond.

4. Immune System

In the essence of preserving their energy, the immune system of your koi fish will also slow down. This is the biggest threat to them, especially when they get sick during the hibernation period.

However, there is an even bigger threat when winter is over as the bacteria and parasites will become extremely active when the immune system of your koi fish are working normally.

You do not have to worry much when they are in hibernation mode as the parasites and bacteria are also most likely not on full alert. It is only when the temperature shifts that you should pay close attention to the health of your fish.

We will discuss this later on, so just keep on reading!how to help my koi fish hibernating?

How Can You Help Your Koi Fish That Are In Hibernation?

Now that you know what happens to your koi fish when they hibernate, it is now time to know how you can assist them in doing this process properly. In this way, they will be prepared when they go into a state of torpor and that they will be healthy afterward.

1. Always Check The Water Temperature

When the winter season is just around the corner, you should start constantly measuring the temperature of the water in your pond. Once it goes below 45 °F, your koi fish will start to go in hibernation mode.

Therefore, even before the water temperature reaches this level, you should start doing preparations to ensure that the pond is in good condition. We highly recommend reading our koi fish temperature guide here!

2. Reduce Feeding

This is in relation to the previous point wherein you should check the temperature. If the temperature is 55 °F or above, you can still feed them the normal amount. However, if you notice that the temperature is dropping, you should gradually reduce their food.

Even before the temperature reaches 45 °F, you should have stopped feeding them.

In the event that you failed to do so and some of your koi fish still managed to eat to their hearts’ content, they will find it hard to slow down their metabolic process and they will struggle during hibernation.

If you feel uncomfortable with not feeding you koi fish, read our article here. It will explain how long koi fish can actually go without food!

3. Clean The Pond

You should make sure that the pond is free from bacteria and parasites. You can do a water treatment, at least two weeks before your koi fish go into hibernation mode.

In this way, there will be not a lot of accumulation of waste that will prompt bacteria to cling to your koi fish once they ease out of their hibernation.

4. Move Your Koi Fish

In the event that you live in a place where the winter season is really tough, and you are sure that your pond will completely freeze, you should consider moving your koi fish into an indoor pond or even individual tanks.

In this way, they do not have to cope with the harsh cold temperature of the water.

You can then just simulate the temperature in the tank so that they will go into hibernation mode. This is actually the ideal situation so that your koi fish will remain healthy and you can easily observe them.

5. What about baby koi?

We have created an entire article about baby koi and winter here! It will show you everything you need to know about that.

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