Everything You Need to Know About A Pregnant Goldfish

Your goldfish might already be mating and before you know it, the eggs have already hatched. Worse, your goldfish might’ve already eaten their offsprings! So, let’s help you determine the breeding cycle.

It is easy for many beginners to overlook signs of reproduction among goldfish. Consequently, they fail to notice that they already have a pregnant goldfish until it is all too late. When this happens, there are high chances that your mature goldfish will eat the eggs.​

What can you do to prevent this from occurring? How can you keep your goldfish healthy during the mating cycle? Find out below!

When Do Goldfish Breed?


In terms of age, goldfish may begin breeding as early as their first year. However, it is best to breed them at three years old. Meanwhile, in terms of size, they begin breeding as soon as they grow four inches long.

Goldfish reproduce at high water temperature. They begin breeding at a water temperature of at least 68 degrees Fahrenheit. In a process known as spawning, pregnant goldfish start releasing eggs at this heat. They are capable of delivering up to 1,000 eggs. Then, male goldfish release their sperms to fertilize a couple of eggs.

This process usually lasts up to four hours.It is easy to distinguish fertilized eggs from those that are not. The former usually comes in a transparent, golden brown color while the latter comes in plain white.​

How to Sex a Goldfish


Hatching occurs five to seven days following spawning or fertilization at a water temperature of at least 75 degrees Fahrenheit. Then, the fertilized eggs are hatched in a week. When the water temperature hits at least 84 degrees Fahrenheit, they are hatched in roughly 54 hours.

How To Look For A Pregnant Goldfish

Like with us, humans, you will know that a female goldfish is “pregnant” when her belly swells as the eggs swell. However, technically, female goldfish do not get “pregnant” because the eggs are not carried in the womb of a female goldfish for fertilization. You will notice the swelling of one’s belly once she is about to deliver the eggs.

A pregnant goldfish looks more rounded than a male goldfish. Then, a protruded vent indicates that she is ready for spawning.​

However, among goldfish, even the male counterparts go through some changes during breeding. Do not be surprised if you see white bumps in their pectoral fins and gill covers; it is all but part of the process.

Aside from physical indications, male goldfish also exhibit changes in behavior. Out of their desire to get started with the fertilization of eggs, you will notice them chasing pregnant goldfish often. When they do, they usually bump their counterparts’ belly and sides.

Nevertheless, constantly chasing and pursuing a female goldfish may be stressful for her. Mainly, the aggressiveness will affect her immune system. If a male goldfish lingers around her for over seven days, you need to give her a break by moving her to a separate tank. Give them a couple of days apart.

How To Take Care Of A Pregnant Goldfish

Before the breeding starts, remember to place a spawning mop in your fish tank. This will allow you to detect and catch the released eggs easily. More importantly, it will help create an organic experience for your pregnant goldfish, and that is around aquatic plants.

Create Your Own Spawning Mop

When making your own spawning mop, you will need the following materials:

  • A4 hardcover book
  • Pair of scissors
  • Dark green acrylic yarn
  • Water in a pot
  • Wine bottle cork

Easy DIY Spawning Mops

After gathering these materials, do the following steps:

  • Boil the dark green acrylic yarn. The purpose of this step is to sterilize the wool, making it 100% safe for your pregnant goldfish.
  • Open the A4 hardcover book. Place the end of the sting right behind its cover.
  • Wrap the yarn roughly 50 times around the book’s length.
  • Cut off the sting to the yarn from the book.
  • Cut a 5” sting piece, which you will tie around the middle of the 50 strands to keep them together.
  • Turn the book over.
  • Cut the yarn around the back right, creating two strands of equal length.
  • Using the loose strand on the top, tie the wine bottle cork. This will allow the spawning mop to float in the water.
  • Lastly, place it in the fish tank where you shall conduct the breeding.

Well, there you have it— an easy step-by-step procedure on how to resemble aquatic plants in natural habitats.

To-Do List For Breeding Your Goldfish

To ensure that the breeding occurs and that your goldfish remain nourished, there are some things you need to do aside from raising and/or adjusting the water temperature regularly:

1. Feed pregnant goldfish more often than you normally would, especially with a protein-rich diet. The likes of bloodworms, brine shrimp, daphnia, among others should always be included in their meals. Then, balance the diet with fruits and vegetables to keep them healthy.

2. Feeding your goldfish with more food may lead to them excreting more waste. So, it is highly recommended that you change at least 20% of the water daily.

3. At least three days prior mating, you might want to separate your male goldfish from their female counterparts. By doing so, they will have a greater longing to mate. Consequently, you will need a second fish tank.

4. After three days, reintroduce your male goldfish to the first fish tank.

5. Continue the frequent water changing, at least until you have returned your goldfish to their normal diet.

Goldfish Spawning


Goldfish breeding is not that hard. As long as you know the basics, you are good to go. So, let us have a quick recap.

Goldfish breeding involves two key procedures, which are as follows:

​1. Spawning, during which female and male goldfish release eggs and sperms, respectively, for fertilization.

2. Hatching, during which the fertilized eggs are hatched.​

Spawning starts at a water temperature of at least 68 degrees Fahrenheit while hatching occurs at a water temperature of at least 75 degrees Fahrenheit.

When the breeding cycle starts, you have to place a do-it-yourself (DIY) spawning mop in your fish tank. This is a crucial part of the process to create a natural breeding environment for your goldfish.

To take care of your goldfish during the breeding cycle, you need to add more protein to their diet. Additionally, you need to change water regularly. More importantly, you need to be mindful of the behavior of male goldfish.

I hope that this article answers all your questions about goldfish breeding. If you have further concerns, you may leave your comments below.

Thanks for reading!

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Jennifer Wood

Hi there, my name is Jennifer Wood, founder of Eforpets.com - a great resource for pets lovers.

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