How Do Koi Fish Mate? Do They Dance

10 min read

how do koi fish mate

Koi fish are amazingly beautiful fish and are great for people to watch. They are very popular for backyard or scenic ponds where people can relax in peace or with friends while having afternoon tea and discussing their life’s philosophy

If you are interested in producing more koi fish on your own or are just interested in how they interact with each other, one question that pops up is, “How do koi fish mate?”

To mate, the female koi fish will release her eggs during the springtime or early summertime (starting around March). The eggs will then be fertilized by one or several males. This is usually preceded by the males chasing the females a lot or more than usual, usually around spring or early summer. You will notice the female’s waistline swelling and the males will develop little white spots called tubercles.

Okay now that you have your answer you can go do that shopping you needed to get done or if you want to learn more, put on your swimsuit, and let’s dive in (no pun intended).

Planned Mating and Breeding

If you heard that koi fish can produce thousands of eggs at a time then you heard right. If you think because of this that it should be easy to raise and sell a lot of koi then you are mistaken.

First, it would take a great amount of time to deal with this many koi. It would also take a huge amount of equipment and you would have to feed them!

A lot of the koi you were raising would have to be disposed of so the cost of the equipment and feeding them would be lost. If you wanted to sell your koi to dealers at this point, they probably wouldn’t want to pay you enough for a decent profit because you are competing against koi farms that have very large operations.

We’re not trying to scare you from mating and breeding your own koi but trying to warn you about doing it for a profit with a small operation.

How to Mate and Breed My Koi Fish

If you just want to mate and breed your own koi fish to add to your pond it is easy to explain, but let’s start from the beginning.

The male koi will be ready for mating when they are at least two years old. Females need to be a bit older so at least three years old. Females’ primary breeding age is between 3-6 years, but they have been known to mate up to 15 years old with success.

If you try to breed koi that are younger they will not be mature enough and their bodies are not ready. Also, if your koi are too young you won’t know if they have the colors that you want to reproduce or if they are your best koi fish.

You want to use your best koi fish for health and color but if you have a limited number and are not concerned about appearance, but only wish to watch them swim around then don’t sweat it.

If you have more koi than you want to use in the breeding process, or if you have really colorful koi that you want to breed, you will need to separate the koi fish that you want to breed from the rest of the fish in the pond.

If you don’t, then all of the male fish will try to fertilize the eggs and you will end up with a wide array of colors that you may not have intended. You can either put a divider into your koi pond to separate the fish or you can remove the koi fish that you want to breed and put them in their own holding tank.

Some people that breed koi professionally have a separate breeding pond.

When you choose the koi fish you want to mate choose the ones that have the most vibrant colors. Don’t use a very attractive koi fish if you plan on selling it in the future or if it is your child’s pet, or just a koi fish that you really appreciate the appearance of. The reason why is the koi fish will end up with torn fins, bruises, and cuts and may even die during the entire mating and breeding process.

You will obviously need at least one male and one female fish to mate. However, it is recommended to have at least two male koi fish placed with the female fish to ensure successful mating and breeding.

Getting koi to mate can be very difficult if they are not in the proper breeding conditions especially if they are younger or too young.

When the males are ready to mate and breed, you will see tubercles that appear as white spots. You will see these white spots on their pectoral fins which are the pairs of fins located right behind their head.

You may also see some on the gills and other fins as well but the main area to keep an eye on are the pectoral fins, just make sure you don’t confuse these white spots with the health ailment which is actually called ‘white spot’.

This will all usually start around March because as stated above, koi fish will begin mating during spring or the beginning of summer. If you know anything about koi yet, you know they practically hibernate during the winter to keep warm and survive.

So, common sense tells us that they want to have their babies when they are awake and during good weather which would be mutually beneficial to them both.

At about the same time the male develops his tubercles, the female will swell around the middle indicating that she is carrying some eggs.

You will also notice during this time of year, if your koi fish are ready to mate, the male koi fish will start chasing the female koi fish quite a bit. The closer they get to mating the more frequently the male will chase the female.

Koi Pond Requirements

Your pond needs to be 3 feet (0.91 m) deep and 6 feet (1.8 m) by 8 feet (2.4 m) foot wide for just 5 koi fish alone. If your pond is too small, you may just need to remove the male koi from the pond until the mating and breeding process is done.

If you are serious about breeding your koi fish, you should install a specialty breeding filtration system during the mating and breeding season to keep the water extra clean. The water temperature also needs to be between 17 to 26 degrees Celsius. Depending on where you live, you can put a pond heater in your koi pond if you are worried but 17 – 26 degrees is easy to maintain so a heater is probably not needed unless you live somewhere like Alaska.

koi fish mating pond

You can use a skimmer net to clean debris and remove unwanted fish that may be predators from your pond. It is also wise to get a net designed to cover your koi pond during mating and breeding season to keep predators away from your koi fish.

You can put a fry mat at the bottom of your koi pond to help ensure the successful mating and breeding of your koi fish. This is a mat that is specially designed for koi fish to use for mating and breeding. It is a sticky mat that will help hold the sinking eggs in place after they sink.

Koi fish sometimes will not mate if they can’t find a suitable place to lay their eggs.

Koi Fish Feeding

You need to feed your koi fish properly during mating and breeding. It is wise to feed your koi fish four times per day. Feed them four times a day but no more than they can eat in five minutes, so you don’t end up with extra uneaten food floating around your koi pond.

You should also feed them extra protein during breeding and mating. The easiest way is to buy a protein supplement for koi or goldfish from your pet store to mix in with their regular diet of koi fish flakes or pellets. Wholegrain bread, green lettuce, and oranges are good treats to supplement their diets.

Separate Mating and Breeding Tank

If you just want to mate and breed one female koi then a 100-gallon tank should be enough. However, if you are planning to breed 2 females with more than five males then you will need a much bigger area. You would actually need a separate breeding pond but that would be for someone wanting to have their own mating and breeding business that produces a lot of koi that you are going to sell or get rid of.

So, let’s assume you are a private owner that just wants to mate and breed some koi fish to add to your own personal pond. Just grab a 100-gallon tank and let’s go.

You can use this tank for the mating and breeding process, but you can also use it to raise the baby koi during their first weeks.

The water temperature in your tank should be the same temperature as the water in your koi pond to make the koi fish feel like they are at home. The water needs to be kept very clean to encourage mating and there needs to be something for the eggs to attach to because as stated above, the koi fish may not mate if there is no place to lay their eggs.

We already talked about the fry mat, but you can also use aquarium plants that are hardy, bristle brushes, or spawning mops. You can also use Spanish moss or bristle brushes from your local pet store.

Spawning Mops – You can look up on Google how to make your own spawning mop or just buy one from your local pet store.

Hardy Aquarium Plants – These are just aquarium plants that survive under the harshest conditions and have a reputation as lasting longer than other aquarium plants. They will have your koi eggs attached to them and you don’t want them to die so that is why you should use hardy plants.

Whatever is used for the eggs to attach to, it should cover two-thirds of the tank.

Once the mating and fertilization of the eggs is done the parents must be removed because koi fish will eat their own eggs. You can simply place the adults back into the pond.

How to Identify Male and Female Koi Fish

You can tell the sex of your koi fish from their fin shape and their color. Male koi fish have fins that are smaller, and you cannot see through their fins. Female koi fish have fins that are larger, more round and you can actually see through them.

If you can’t tell the sex from the fins look at the koi fish body. Females have a wider body because they will be carrying eggs at some point while the male fish is longer and skinnier. This is actually why female fish are used for show fish because people find the wider body more attractive.

How Often Do Koi Fish Lay Eggs?

The female koi fish can lay eggs twice a year in their natural environment. The first time they lay more eggs than they do the second time. This is primarily between 3 – 6 years old although female koi fish have been known to lay eggs until they are fifteen years old.

How Long Are Koi Fish Pregnant?

Technically koi fish don’t get pregnant since they don’t carry babies. However, they can carry thousands of eggs for up to a few months until they release the eggs for the male to fertilize. The eggs sink and attach to something in the bottom of the pond where they grow outside of the female.

How Many Eggs Do Koi Fish Lay?

Scientists say that female koi can carry approximately 100,000 eggs for every kilogram of their body weight. Even if the female koi fish lays all of these eggs, only about 60 percent will survive.

What Age Do Koi Breed?

Female koi fish breed primarily between the ages of 3-6 years old. Some have bred up till the age of 15 years. Male koi fish are ready to mate at two years of age.

Koi Fish For Sale

Just type ‘koi fish for sale’ into Google and a map will automatically pop up that shows you where the nearest koi dealer is.

How Many Babies Do Koi Fish Have at A Time?

Koi fish do not have babies. They release around 100,000 eggs per kilogram of body weight for the male koi fish to fertilize. Scientists say only 60 percent of these eggs will survive. So you can say, female koi fish can produce around 60,000 babies per kilogram of body weight but only if the male koi fish fertilizes all of the eggs.

What Do Koi Eggs Look Like?

It depends on if they are fertilized or not. If the eggs are not fertilized they are white. If the eggs are fertilized, they are light brown, and you can see two eyes soon after they turn brown. If the eggs get a white fungus on them then something is wrong so light brown is good and white is bad.


This article is about how koi fish mate. I tried to completely answer the question for you in case you were planning on trying to mate your own koi fish or were just interested. They simply mate by spreading eggs and fertilizing them but there is a lot more to it than that. It is a process to get them to actually mate which I hope I thoroughly explained.

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Pet Aquariums

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