How Many Babies Do Koi Fish Have at a Time? {How Often?}

Is your koi fish pregnant and full of eggs? How many babies do koi fish have at a time?

How often do koi fish lay eggs?

You will find detailed answers to these questions and many more in this article.

How Many Babies Do Koi Fish Have at a Time?

A female koi fish can carry about a hundred thousand eggs for every 1 kilogram of body weight.

  • A 5-kilogram female koi fish will take about 500,000 eggs in her.
  • Koi fish have a 60% hatch rate.
  • A 5kg koi will have 300,000 babies at a time.

How Many Babies Do Koi Fish Have at a Time

How Long is a Koi Fish Pregnant?

Technically, koi fish do not get pregnant because they lay eggs and do not give birth to their babies alive. They only carry their eggs in them until they are ready to fertilize them.

Koi fish can surprisingly be pregnant with their eggs for about one year.

  1. The female starts forming the eggs in her body and lays them during the male koi breeding season to fertilize them.
  2. The males usually encourage the females to drop the eggs during the spawning season.
  3. The female-only starts to develop eggs when she becomes mature.
  4. It takes about a year for her to develop the eggs ultimately.
  5. Once the eggs are ready, she might still carry them for days, depending on how she wants the egg fertilized.

As soon as they drop the egg, they start developing another set of eggs, leaving the males to do the fertilization.

How Often Do Koi Fish Lay Eggs?

Spawning in koi fish is usually an annual activity for koi fish, which means they will breed and lay eggs once every year. Some koi will spawn and lay eggs twice a year.

The first set of eggs will be more than the latter group of eggs. Usually, when they spawn during spring, the next time they will breed is the coming spring, unless in rare cases when they spawn twice a year.

Spawning usually occurs during:

  • late spring
  • when the water is warmer

Koi fish will:

  • lay their eggs
  • start repairing for the next spawning period.

You have to provide the adequate requirement for your koi fish to enhance their spawning activities.

YouTube video

Best Water Temperature for Pregnant Koi Fish

The best water temperature that supports koi fish breeding is:

  • 68 degrees Fahrenheit

The temperature can vary a little with slight variations, and the fish will still reproduce.

When the temperature goes extreme, the koi fish might not find it suitable to spawn as the female might not even lay her eggs in the first place.

The water’s pH also has to be favorable for koi fish to spawn as the females will not want to lay their eggs in an unconducive environment.

You have to make the water clean and free from dirt to create a good spawning site for your koi fish. Your koi fish will spawn and lay their eggs at the right time if you provide the proper condition.

How Many Koi Fish Eggs Will Hatch?

The number of koi fish eggs that will hatch depends on the number of eggs laid. The amount of eggs laid is dependent on the body size and weight of the koi fish.

When a female koi fish lays her eggs, roughly 60 percent of the eggs will hatch into baby koi.

  • Female koi fish will lay about hundred thousand eggs per kilogram of body weight.
  • It means a 10-kilogram female koi fish can lay up to one million eggs.
  • Only about 60 percent of the eggs laid will hatch into babies.
  • It means when a 10-kilogram koi fish lays her eggs, only about 600,000 eggs will hatch into baby koi fish. 

The number of eggs provided by the female koi fish can vary; it can be more or lesser than the stated figure.

How Many Eggs Do Koi Fish Lay?

Koi fish can lay incredible numbers of eggs at once.

  • A female koi lays up to 100,000 eggs at one pound of weight.
  • Most of the time the number hovers around 50,000 eggs.

Usually only half of these eggs will survive and fewer will make it through the fry stage. If the female koi fish is sexually mature and has reached the weight of 2 pounds, she can lay up to 100,000 eggs during this breeding season.

This is how professional koi fish breeders estimate how many eggs a female can lay by weighing her first. A general rule of thumb is:

  • 1 lb of female koi fish weight =  approx. 50,000 eggs.

When Do Koi Fish Breed?

The time of the year is very important to koi fish breeding. The temperature is also very important as well. Ensure that the water reaches about 65-70 degrees Fahrenheit or there will be no breeding season this year.

  • The time of the year is about late spring to the early summer.
  • May and June are the most popular times when koi fish breed.

They must reach sexual maturity first which happens at about two years of age or when you notice that their length is about 12 inches.

Breeding koi fish is a tough task, but would be easier once they reach about 4 to 5 years of age. Spawning for a young koi fish is stressful and it can damage their health.

How Many Times Do Koi Fish Lay Eggs?

Spawning is usually occurring during the seasons of late spring or early summer. The best time for the maximum amount of eggs to be spawned at once occurs when the temperature is at the mark of 65-70 degrees Fahrenheit.

  • Koi fish mate usually once every year
  • It lasts up to 6-7 years once they have become fully mature.

Some koi fish breeders are trying to get their koi fish to spawn 2 times a year, but when this happens she will lay fewer eggs each time.

You will most likely notice female koi fish laying eggs in the early morning. Before female Koi fish lay eggs, you will notice the male koi fish following them and showing a lot of interest. It’s natural for a koi fish to lay eggs only once a year.

What Do Koi Eggs Look Like?

Koi fish are large in size, but their eggs could be:

  • tiny little bead-like specks
  • milky white
  • yellow
  • green
  • containing black dots through the membrane of the egg

Those two dots you are looking at are the eyes that are developing inside the eggs.

The first few hours after spawning, the eggs are very tiny. They could be as small as a few millimeters, but they look just like tiny little beads.

Most of these eggs will not be fertilized, and less than half will probably survive. That could be a good thing because a female can deliver up to 50,000 to 300,000 eggs at one point.

YouTube video

What Do Baby Koi Fish Look Like?

Baby koi fish:

  • do not look much like their parents or any adult koi fish
  • tend to have a dull appearance with an almost plain brown color.
  • difficult to differentiate from other small aquatic animals.

Their dull colors serve as a protective measure against predators as bright will portray them as a meal to other fish. The koi baby fish are tiny that you cannot determine the type of pattern they will grow to have.

You have to protect the baby koi fish from predators as their small size will make them easy prey for hungry fish.

Do Koi Fish Eat Their Babies?

Koi fish will eat their
babies when they are still eggs or very small and resemble small insects. They eat their babies not because they are aggressive or cannibalistic but because they do not recognize them.

The babies:

Once the baby koi fish starts to grow into adult fish and start to look more like their parents, the koi fish will stop eating them.

You will start to notice the koi fish eating the eggs or babies right from when the spawning starts. Mothers will even eat their eggs when they come across them due to the stated reasons.

Why Are My Koi Eggs Turning White?

When your koi eggs turn white, it means:

  • there is a problem with the egg
  • it will prevent the eggs from hatching into baby koi fish
  • they have not undergone fertilization
  • infected by fungi

When the male does not properly or completely fertilize the female’s eggs, the eggs start turning white after a while. Without being fertilized, the eggs will not hatch into baby koi fish, making the egg a waste of time and resources.

Koi Egg Fungus

Fungi infestation usually occurs when the male does not fertilize the egg. Unfertilized eggs are prone to fungi attack and will cause trouble for the other fertilized eggs.

The unfertilized eggs attract fungus, and when the fungus affects them, they move to the fertilized ones to continue the job they started.

Once you notice the attack from fungi on any egg, you should remove the tank’s eggs to avoid getting other koi eggs affected. Make sure you provide adequate water conditions for the eggs to prevent them from any problem.


Koi fish can have many babies ranging from thousands to hundreds of thousands of babies. The amount of babies they can have depends on the capacity of the mother.

Make sure you take the mother to have a large capacity, and she will provide you with many babies.


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Hello, I'm Jason. I'm the guy behind I volunteer at my local fish shop and I created this site to offer tips and advice on the fish I care for.