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Home > Goldfish > How to Breed Goldfish: Vet-Approved 10 Step Guide for Successful Breeding

How to Breed Goldfish: Vet-Approved 10 Step Guide for Successful Breeding

Goldfish In a tank

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Dr. Luqman Javed Photo

Written by

Dr. Luqman Javed

Veterinarian, DVM

The information is current and up-to-date in accordance with the latest veterinarian research.

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Breeding goldfish may seem like an exciting way to make goldfish keeping even more enjoyable. The journey to breeding goldfish is tricky, however, and you should ensure that you have the time and money to spend to produce healthy goldfish offspring.

Goldfish are prolific breeders, and therefore, the decision to breed your pet fish shouldn’t be taken lightly.

Successful goldfish breeding will involve several factors, including the parents’ lineage and history of illness. It is best to choose healthy goldfish with good morphology and no history of previous health issues like swim bladder disorder, tumors, or a poor body condition score.

This is a complete guide full of tips and tricks to help you breed the healthiest and most beautiful goldfish offspring.


The Ethics of Goldfish Breeding

Please note that the information in this article is for informational purposes only. At Pet Keen, we do not encourage breeding your goldfish. A single female goldfish can lay up to 1,000 eggs in one spawning session and over 10,000 eggs per breeding season. Females are also prone to being injured during the mating season, and the process places a very high demand on your fish.

You need vast numbers of tanks,a lot of money and time, and ample preparation before goldfish can spawn. It is also important to note that the process comes with its fair share of heartbreak as most fry (baby goldfish) are eventually culled. It is naive to assume that all your goldfish can be successfully rehomed. This is not a quick or easy way of making a monetary profit. It is best to leave breeding goldfish to a professional breeder.

As with all animals, there is the worry of ethics in purposefully breeding already inbred goldfish varieties. Goldfish are plentiful in the aquarium world and are one of the most popular pet fish kept as pets. This means that there are a lot of goldfish out there looking for good homes. Although there are not many ‘rescues’ that take in abandoned goldfish if any, and you should have an ethical reason for wanting to broaden the goldfish population.

A good mindset for breeding goldfish is to produce quality specimens with few health issues and an overall show quality body and coloration. This will draw in potential buyers who are searching for a breeder who has excellent stock that has been bred for all the right reasons. Goldfish owners want a goldfish that will experience minimal genetic issues later in life and grow to their full size while reaching close to their full lifespan potential.

Image Credit: panpilai paipa, Shutterstock

The Cost and Equipment Required to Breed Goldfish

Breeding goldfish is a very expensive task, it will usually cost more to cater to their care than the overall profit you can make from the breeding industry. This is because goldfish will eat their eggs and their young. This makes them poor parents and goldfish parental care is non-existent.

It means you would have to purchase extra tanks and equipment to not only incubate fertile eggs, but you will also have to move eggs and fry to different cycled tanks to avoid them from being eaten by larger goldfish who only see them as a quick meal. You will have to equip each tank with an air stone and filter and take on the parent role. You will also need to perform daily water changes and have separate tanks to rear live food for the young.

A basic essential kit to get you started in the goldfish breeding hobby is to purchase the following:

  • A 5-gallon medicating tank
  • Multiple 20-gallon tanks at minimum (for spawning)
  • Multiple other small tanks to raise fry in
  • Bushy and smooth aquarium plants (live or fake)
  • A good sponge filter with a low current
  • An aeration system (spray bar, air stone, bubbler)
  • Fry foods – these require their own tanks to be raised in
  • Spawning mop (optional)
  • Aquarium chiller
  • Aquarium heater
  • Correct male-to-female ratio of goldfish
  • Copper sulfate (prescribed by your veterinarian)
  • Formaldehyde (prescribed by your veterinarian)
  • A broad-spectrum antibiotic (prescribed by your veterinarian).

Once you have set up the tank and equipment, you are ready to begin breeding your goldfish!

If you're new to the world of goldfish keeping or are experienced but love to learn more, we highly recommend you check out the best-selling book, The Truth About Goldfish, on Amazon.The Truth About Goldfish New Edition

From diagnosing illnesses and providing correct treatments to proper nutrition, tank maintenance and water quality advice, this book will help you to ensure your goldfish are happy and to be the best goldfish keeper you can be.

two goldfish veiltail
Image Credit: Pixabay


The 10 Step Guide to Goldfish Spawning

1. Plan A Year Ahead

Goldfish can breed at the age of one to two years old. If you are planning to breed goldfish, it’s important to raise them for at least a year before deciding to do so. If you have a young goldfish, you can also watch for illnesses and genetic failures that will occur in the goldfish as it matures. This will help you to see the genetic potential of the goldfish by their health, size, coloration, and body shape.

goldfish in aquarium
Image Credit: seaonweb, Shutterstock

Keep an eye on potential fish you wish to breed, and try to identify them by July or August (goldfish are spring spawners, and prospective parents should be identified by autumn of the previous year). It is a good idea to keep records on any health issues and problems that may occur in your goldfish so you have a good idea of which specimens will make great breeding stock.

2. Seek Professional Input

Once you have identified the fish you wish to breed, have an aquatic veterinarian come and inspect your fish. Alternatively, if you’re not sure which fish should be bred, it’s best to let your veterinarian decide for you. Remember that a fish that looks appealing might not have the best traits of a robust breeder.

The ideal ratio for spawning goldfish is 3 males to every female. If you haven’t sexed your goldfish, you should ask your veterinarian to do so. Your veterinarian may also run blood tests on your fish and advise you on breeding compatibility.

Please note that the health of your female goldfish is very important, as they can easily get injured during the spawning season. If you have a beloved female goldfish, it is best to not breed her.
It is also best to discuss the option of artificial insemination or hand spawning with your veterinarian at this point; many aquatic vets are able to provide this service for a fee. Though it requires additional monetary investment, it minimizes the risk of injury for female fish and increases the number of eggs that are fertilized.

3. “Clean” Breeders

You would want to place the breeding stock in their own large, cycled aquarium. Before doing so, provide each fish with a “cleaning” cycle by placing them one by one in a 5-gallon aquarium and adding in a combination of Formaldehyde, Copper Sulfate, and a broad-spectrum antibiotic (prescribed by your veterinarian).

Image credit: pritsana, Shutterstock

The dose of Formaldehyde and Copper Sulfate should be discussed with your veterinarian, as the amount you need will vary depending on the concentration of the product you have. The duration of their exposure to the cleaning process should also be discussed with your veterinarian. It is recommended to have your veterinarian perform this procedure for you.

4. Condition In Aquarium

Once your breeders are in their aquarium, it is important to begin conditioning them with foods such as brine shrimp, worms, and a high-quality pellet.
Important: Do not change their diet abruptly, but rather add these food items into their diet gradually.

It is best to feed your goldfish small amounts of food several times a day (three to four times) when conditioning them this way. When feeding your goldfish for the purposes of breeding them, you should feed them as much as they can eat in a few minutes. It is very important to not let leftover food in their aquarium, as this may spoil and degrade the water quality of your breeders’ housing aquarium.

Live food fed to breeders should be sourced from a reputable breeder, as feeding poor-quality live food offers lower nutritional value and may introduce unwanted pathogens into your aquarium.
Your breeders will need to be constantly conditioned from their selection day up and even after they are done spawning, as the process is quite draining on their bodies.

5. Simulate Winter

As goldfish are coldwater fish, they spawn in the springtime. Waiting for seasonal changes can be cumbersome and when breeding goldfish, it’s best to use a chiller to manipulate the temperature.
Winter can be simulated by gradually dropping the temperature in their aquarium to 10 – 12°C (50 – 54°F). You should only decrease the temperature on your chiller by 1 – 2°C (1.6 – 3°F) per day.

Note: your fish will naturally stop eating as temperatures drop and go into a state of near hibernation, called torpor.

6. Simulate Spring

When you are ready to breed your fish, it’s time to simulate springtime. This time, you’ll need a heater to slowly increase the temperature in their aquarium by 1 – 2°C (1.6 – 3°F) per day until you reach 20 – 23°C (68 – 74°F). This process takes about a week or so.

7. Isolate Best Breeders

Begin to identify prospective breeders in your breeder tank. Males that are ideal for spawning should develop small white dots on their gills and heads (known as tubercules), be strong swimmers, and should show interest by chasing females around. Females that are ideal for breeding should be larger than males, and should slowly turn plump.

Image Credit: Last 4ever, Shutterstock

Isolate a group of 3 males and 1 – 2 females in a 20-gallon spawning aquarium. Ensure it is cycled and maintained at the “spring” temperature.

Important: A 20-gallon aquarium cannot sustain 4 – 5 spawning goldfish for a long period of time and needs daily partial water changes of 20 – 25% to maintain water quality.

8. Wait For Eggs

Observe your females in the spawning tank, as the stimulation from the males eventually makes them drop their eggs, which stick onto the surfaces of the spawning tank. They usually drop their eggs on the plants in the spawning tank.

Once a female drops her eggs, the males fertilize them by releasing their sperm into the water (fertilization is done externally).

9. Remove Adults or Mop Eggs

Remove the adults from the spawning tank, or move the eggs using a spawning mop. You might be able to identify fertile eggs from infertile ones:

  • Infertile: The eggs will go a deep white color and have no black dots signaling the eye development of the goldfish in the egg. They will begin to rot after a few days and produce a fluffy fungal coating. The eggs should be disposed of with warm water and a methylene blue solution in the breeding tank.
  • Fertile: The eggs will be a transparent pearl color and have black dots as the goldfish’s eyes develop. The eggs will hatch after a few days and will even show the outline of the fry if a torch is shone on them.
yellow round goldfish egg material goldfish eggs
Image Credit: stockt0_0, Shutterstock

Eggs take 4 – 7 days to hatch; eggs that don’t hatch after 8 days are considered infertile. Infertile eggs should be removed from the aquarium, as they will rot and degrade water quality rapidly.

10. Monitor Fry & Care For Adults

Newborn fry can be fed baby brine shrimp or other foods small enough to fit in their mouths. You can begin the process of raising fry soon after they’ve hatched. Congratulations on your spawn!
Please note that you should also keep an eye on your spawning fish. Females may get injured during the mating process and might require additional care.


Reasons Behind Goldfish Breeding Failure

Sometimes you may run into trouble when trying to breed your goldfish and this is called breeding failure. It is rare, but sometimes goldfish will not breed. If you have followed all the steps to ensure all the right conditions and breeding requirements have no been met, here are a few reasons your goldfish are not breeding:

  • Your goldfish are too young and not sexually mature.
  • You have the wrong ratio of males to females.
  • The goldfish have been sexed incorrectly and you may have mistaken a male goldfish for a female or vice versa. Your veterinarian can help circumvent this by correctly sexing your fish.
  • The tank has not been conditioned to stimulate natural breeding triggers.
  • The fish are stressed or ill.
  • The female becomes egg-bound and requires immediate help from a professional. She will have trouble depositing eggs and show various health issues as the eggs begin to foul in her reproductive tract. You should immediately contact your veterinarian if you suspect this is the case.
  • The male or female goldfish are experiencing infertility problems and may require supplements or medication from a veterinarian.
  • Your goldfish are suffering from nutritional deficiencies from an inadequate diet.



While breeding is fun and a great way to better the genetic lineage of your goldfish, it does require certain expertise and a massive commitment. Once the eggs hatch, you will then begin caring for the cute mini versions of the adults. Raising fry is an enjoyable experience and will help you follow the full development process of the stock. If you know the basics of good goldfish care, while having much experience in caring for them, you are ready to become a successful fish breeder!

Featured Image Credit: panpilai paipa, Shutterstock

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