What You Need To Know About Pregnant Koi Fish Behaviour

Koi fish are beautiful fish that are growing in popularity as the years go by due to their beauty. However, when the female Koi fish become pregnant, their behavior can change, and if you don’t know what this change in behavior means, it can be quite concerning for you. So, here is everything you need to know about the behavior of female Koi fish.

Female Koi fish behavior can change noticeably when they are pregnant. The female Koi will go through pre-spawning before they drop their eggs. During this time, they will require more feeding, hide more, stick to the pond’s rocky and plant-filled areas, and begin cleaning the area.

How long do pregnant female Koi fish carry their eggs? How do you correctly take care of a pregnant Koi fish to ensure the health of the female Koi and her eggs? Let’s find out!

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Behaviour Of Pregnant Koi Fish

Pregnant koi fish

When people think of a Koi pond, they imagine a scene of calm, peace, and serenity. This is generally what a Koi pond is like through most months of the year, but there comes a time when this calm scene is interrupted.

This is when the Koi fish are reproducing, and the female Koi fish are looking for a place to drop their eggs in the tank or pond you keep them in. When your female Koi fish are pregnant, they will display some behavior quite different from their normal behavior.

This behavior can also trigger some unusual behavior in your male Koi fish. You will easily notice the pregnant females’ change in behavior, so it’s not something that you have to worry about not noticing.

When they are pregnant, the female Koi fish’s behavior is one of the most noticeable signs that Koi breeders look for to identify if their female Koi are pregnant or not. Let’s take a look at the behavior of the pregnant Koi fish.

The Pre-Spawning Behaviour Of Pregnant Koi

Pre-spawning behavior is the first noticeable change in your female Koi fish, indicating they are pregnant. Once the female Koi fish is pregnant, she will begin surveying her surroundings, looking for an appropriate place for her to lay her eggs.

Your female Koi fish may begin behaving oddly and will start to gravitate to certain pond areas. You may notice your female Koi spending more time near the rocks and plants in the tank as they search for a place to drop their eggs.

Another noticeable change in behavior that could happen in the pre-spawning stage of your Koi’s pregnancy is that your female Koi might develop a bigger appetite. They may begin chasing other Koi away from food so they have more to eat.

Pregnant females will also want to eat more regularly than usual. The pregnant females may also begin hiding more as they try to avoid the male Koi hounding them.

Koi fish hiding behind pond plant

The Cleaning Behaviour Of Pregnant Koi

The cleaning behavior of the female Koi fish indicates that they are pregnant and are close to laying their eggs for the male Koi fish to fertilize.

When a female Koi fish has formed eggs inside her body, she will begin swimming around the pond or tank, searching for a safe place to lay her eggs; this is the pre-spawning behavior mentioned above.

When the pregnant female Koi finds a suitable location to drop her eggs, she will begin cleaning this area intently.

She will clean the location she has chosen to ensure it’s clear of any loose debris or organisms that may damage the eggs she drops. This will also ensure that the eggs have a good chance of sticking to the places and rocks in that area, further reducing the chances of the eggs being harmed.

The pregnant female will spend a good amount of time cleaning her chosen egg-dropping location, and she is unlikely to leave this location until she has dropped her eggs.

How Long Do Koi Fish Carry Their Eggs?

When you first notice the behavioral changes in your female Koi fish that indicate they are pregnant, you might be wondering how long your female Koi will carry their eggs before they drop them for the males to fertilize.

The female Koi fish will develop and grow their eggs in winter. Usually, these eggs will be fully developed in the late winter. The female Koi will then carry her eggs until spring when the water warms up.

When the water is the perfect temperature in the early spring, the female Koi will begin their pre-spawning behavior and start looking for a suitable location to drop their eggs. So, a female Koi fish will carry her eggs for a few months.

How To Correctly Care For Pregnant Koi

Pregnant koi fish

It is important to look for the signs that indicate your female Koi fish are pregnant before they start spawning, as you will need to change a few aspects of their care to ensure the health of the female Koi fish and her eggs.

If you don’t want your Koi fish population to grow, then watching for these signs can help you separate your female Koi fish from the males to ensure the eggs don’t get fertilized when they are dropped.

Whether you want to grow your Koi population or not, you must care for your female Koi fish correctly until they drop their eggs.

Female Koi fish need to drop their developed eggs when they are ready, as not dropping them can lead to some complications that could affect the fish’s health. So, let’s go through what conditions the female Koi fish need to remain healthy and drop their eggs.

Water Conditions

The conditions of the water you keep your pregnant Koi fish in are an important aspect of the spawning process. If the water conditions are not right, the female Koi will not drop her eggs. The water conditions needed to encourage spawning will be the same in an indoor and outdoor pond or tank.

You mainly need to monitor the ammonia levels and the water temperature to encourage spawning. The water temperature will need to be between 65 and 75°F (18 and 24°C). You must maintain the temperature in this range, or the female will not drop her eggs.

The ammonia level in the water needs to be close to zero, as this will help ensure the eggs’ health when dropped. If the ammonia level is high, the female Koi will avoid dropping her eggs.

Feeding And Types Of Food

Koi fish eating a watermelon

When dealing with pregnant Koi fish, you will need to feed them more regularly than you are used to. Pregnant female Koi fish will require feeding at least four times per day to help keep the females and the eggs they carry healthy.

You also need to ensure that the food you are feeding your pregnant female Koi fish is high in protein as the eggs require protein for healthy development, and this can take its toll on the female if you don’t provide high protein food.

Providing Places For Female Koi To Spawn

koi fish hiding under an aquatic plant

When you see the signs that your female Koi fish are pregnant, you must provide them with places to drop their eggs. You need to ensure enough rocks and plants in the tank or pond for the female to choose from. If the female doesn’t find a suitable location for her eggs, she will not drop them.


Pregnant female Koi fish have some noticeable changes in their behavior, and knowing these changes means pregnancy is important as a Koi fish owner. This can help you control the Koi population you have and can help you ensure the health of your female Koi fish.

Once you notice the behavioral changes in your female Koi, you must follow the guideline above to safeguard the health and safety of the females and their eggs. Good luck with your pregnant female Koi fish!








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