Home » Fish Guides » How To Stop Goldfish From Breeding | This Is How I Did It |

How To Stop Goldfish From Breeding | This Is How I Did It |

Goldfish are not like livebearers who give babies repeatedly, but when they do, they will provide you with thousands of babies at once. Considering that you have limited space, this can be a problem for most aquarium owners. But how to stop goldfish from breeding?

As much as you love your goldfish, you will love its babies too. But, you have to get rid of those babies for the sake of your much-loved pet, as an overstocked tank is not a healthy tank for your goldfish.

Fortunately, you can prevent your goldfish from breeding by following some straightforward procedures mentioned below.

How To Stop Goldfish From Breeding

How do goldfish get pregnant?

Goldfish technically do not get pregnant as they are egg-laying fish.

However, we use the term “pregnant goldfish” for the female fish that carry eggs. When these fish are ready to spawn, the female goldfish develop eggs in her body. This makes her belly larger than other females in the tank.

How long the female carries eggs before they hatch depends on how you care for your goldfish.

If you keep changing their water temperature frequently, eggs will not last long in your goldfish’s belly.

However, if you do not change water temperature frequently, the eggs may stay in your female goldfish’s body for a week or more.

Goldfish are egg layers. So, when the eggs are matured enough to fertilize, the female will spawn with the male.

The female goldfish will lay eggs while the male fertilizes them with its milt (sperm). The fertilized eggs then take about 2 to 7 days to hatch.

Once the eggs hatch, baby goldfish will swim into the water and feed on the egg sacks. The babies will start eating immediately after hatching and grow rapidly under good care within a month or two.

At what age do goldfish lay eggs?

Goldfish sexually mature within 1 to 2 years of age, but they usually don’t reproduce until they are about 3 to 5 years old. So, fortunately, you have a very long time to prepare for the babies or stop goldfish from breeding.

What causes goldfish to breed?

Sudden changes in the temperature are the leading cause for goldfish to breed.

Goldfish are cold-water fish that prefer to live in cold temperatures—these fish spawn during the spring when the weather is warm in the wild.

So, when you replicate these conditions in your tank, it triggers these fish to reproduce. So, if you want to breed your goldfish, you have to set up your tank to10- 12C temperature for a few days. Then gradually change the temperature to 20-23C.

This change in weather will trigger your goldfish to breed.

How do you tell if goldfish are spawning?

The best way to determine if your goldfish are spawning is to observe pre-spawning behavior and signs.

When the male goldfish is ready to spawn, it will develop tiny white bumps around its head. These white bumps are called “spawning tubercles,” and they also grow around gill covers and pectoral fins. However, if you are not a seasoned aquarist, it might be hard for you to notice these spots.

Another sign that your fish are spawning is that the male fish continually chase the female fish around.

If you keep observing your goldfish closely, you will notice that the female fish is bloated with eggs, and she doesn’t like it when the male fish keeps following her around.

Your fish will also refuse food and become aggressive when ready to spawn. And you can see “nesting” behavior from your female goldfish, especially when they are close to laying their eggs.

How often do goldfish reproduce?

In the wild, these fish usually breed once a month during April and August, when the water is warmer.

However, these fish can spawn more than once until the water remains warm. So, if you trigger their spawning once a month all year long, you will have a tough time stopping these fish from breeding.

How long does goldfish breeding season last?

Goldfish naturally breed in the summer, from April to August. So, they can literally spawn for about half a year. If you trigger these fish to reproduce more than once a month, there is no end.

How To Stop Goldfish From Breeding

How many babies do goldfish have?

Goldfish females can lay from 100 to 1000 eggs in one spawn. It will depend on how big your goldfish is most of the time. There is no limit to how many times they can spawn, though. 

How to stop goldfish from breeding?

Unlike livebearer fish that are hard to control, goldfish are, fortunately, easy to handle when breeding.

Since it is possible to differentiate males from females, things are easier. To stop goldfish from breeding, you can efficiently try a few methods below.

Keep only one gender fish

Goldfish can not store eggs like livebearer fish. For goldfish to fertilize an egg, a male and a female fish must be together.

So, if you only have one gender fish in your tank, your goldfish can’t breed. You can either choose male fish or female fish, and you’ll be good to go without the hassle of babies.

Do not fluctuate the temperature (Cold temperature preferred)

As mentioned before, warm water conditions are the leading cause of these fish spawning.

So, if you keep these fish in a cold water tank and you do not change the temperature to a warmer number, then your goldfish will not reproduce.

Keep other carnivore fish in the tank

Keeping other fish that eat fish fry in the goldfish tank is another efficient way to control the population of your goldfish.

These fish usually eat all the eggs and fry that they can find, so keeping them in one tank together is better. This will ensure that they do not reproduce while you are not looking.

How to identify male and female goldfish?

Identifying goldfish males and females is not easier. However, they’ll show behavioral and physical differences when they mature.

Goldfish take about one year to get sexual maturity, but you don’t have to rush separating the fish as they take another year or two to reproduce.

To identify male and female fish, you need to check these signs.

Shape – Female goldfish are shorter and rounder. This round shape is distinct in the abdomen area, and it becomes much more significant when they are ready to spawn.

However, they may also get plumper when there is a bacterial infection. So, you should be aware of that too.

Male fish are longer and thinner than female specimens. They don’t have a distinct abdomen. So, it is usually easier to identify male specimens.

Vent– The part that releases waste (vent) located under the anal fin is a main part that can be used to identify male and female goldfish.

The vent of females is shorter and located at the side of the female. The male specimens have more extended and indented vent than females.

Breeding tubercles– The male goldfish develop small white dots around the head, gills, and fins when they are ready to spawn.

These dots are called breeding tubercles or breeding stars, and it is a good indication that it is a male goldfish.

Dorsal fins– Male goldfish usually have longer and thinner dorsal fins, while female goldfish have shorter and thicker dorsal fins.

Behavior– When the male fish is ready to spawn, it chases the female, pushing and nudging around. On the other hand, females constantly run from the males and have torn fins.

What to do with baby fish you don’t want?

When goldfish are having babies, it will be so much that it is too much for you to handle. If you decide to keep them all, you’ll have to buy a pond at least. So, it is better to get rid of the babies than keep them. 

You can do three things to get rid of unwanted goldfish babies.

  1. Sell them away– You can sell your baby fish to someone who is willing to buy them. 
  2. Give them away– If you do not find a buyer, you can give them to someone free of charge. This will not earn you any money, but at least you get to find a new home for your goldfish babies.
  3. Cull them– Culling fish fry is not humane, but you will have to do it at some point because releasing these fish into the wild is not wise. If you release these fish into the wild, they may invade the local environment and cause harm to the local habitat. So, culling them is the only way out. Although taking these fish out of the water will do the job, you can instead add carnivore fish to the tank to eat the fry. While it can be cruel, this is how it works in nature.

Do goldfish eat their own babies?

Yes. Goldfish may and will eat their own babies, misinterpreting them as food.

Goldfish do not have paternal instincts and don’t recognize their own babies. As they are omnivore fish, it is totally normal for them to eat their own children.


Goldfish are egg-laying fish that lay thousands of eggs at one time. But fortunately, it is not challenging to stop goldfish from breeding.

Simply separating males from females would do the trick, but if you want both male and female fish in the tank, you can prevent spawning by adjusting the water temperature.

Credit to : Your Fish Guide
How To Stop Platy From Breeding | Here Is How !! |
How To Stop Guppy From Breeding | Easier Than You Thought |
How To Stop Mollies From Breeding | A Simple Way |

Sharing is caring!

About Dr.Chamika

Hello, I'm Dr. Chamika. I am a Researcher in Water quality, Aquatic organisms, and Environmental chemistry. I am a passionate fish keeper, with10 years of experience. My mission is to help other aquarists experience the joy of fish keeping.