Goldfish Gestation Period – Is My Goldfish Pregnant?

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Goldfish are awesome tank fish, thanks to their diversity, personality, and adaptability. That being said, they aren’t exactly the easiest to care for and can be a bit tricky to breed.

This is why goldfish aren’t exactly fitting for novice aquarists, especially due to them being more pretentious about their water conditions and the amount of waste they can produce.

When it comes to breeding, the goldfish comes with several unique challenges, such as:

  • Eating their own eggs – As egg layers, goldfish can produce several hundred eggs in one go. More prolific females may also lay in excess of 3,000 eggs in the right circumstances. Then the goldfish will start eating them. This is a problem if you plan to breed your goldfish for profit or breed them selectively to obtain specific characteristics and strains.
  • More males than females – When discussing most fish species, it’s generally recommended to have more females than males. This will reduce male-on-male aggression that’s usually fueled by higher levels of testosterone and the innate predisposition towards mating competition. The problem is that you should do the opposite with goldfish. You need to have several males during the mating season to ensure enough sperm is produced to fertilize as many eggs as possible. Naturally, you should expect a lot of male goldfish violence as a result.
  • Not all eggs will hatch – This may not seem like much, but it’s actually an important point. Unfertile eggs will begin to rot away in the water, increasing the ammonia levels fast. And goldfish are sensitive to ammonia and nitrites since these chemicals can cause significant discomfort, extensive body damage, and even coma and death. This means you will have to handpick bad eggs and remove them from the tank to prevent that. You can tell which are unfit for hatching by coloring; the bad ones are darker, while the fertile ones are lighter.

However, you can breed your goldfish despite all these issues, provided you put in enough thought and effort.

But let’s fill in some common blank areas about goldfish reproduction that you may be facing as a novice.

Can a Goldfish Get Pregnant?

Theoretically, no, since the notion of pregnancy only applies to livebearers. To be pregnant means to have one or more living offspring in the uterus, and goldfish don’t qualify for that.

Goldfish are egg layers, so the female will display signs of pregnancy without being actually pregnant; it’s just that its belly grows larger.

But ultimately, this is just semantics, and we have no other word to describe the female’s egg-laying condition. So, we call it pregnancy.

How to Tell if a Goldfish is Pregnant?

There are multiple signs informing you that your goldfish is getting ready to lay eggs.

These include:

  • Seasonal indicators – Goldfish lay eggs in late winter or early spring in the wild. Even when kept in indoor tanks, they will retain the same behavior in captivity; their biological setup serves as guidance. So, you should monitor your goldfish closer as the winter comes to an end.
  • Mating-specific interactions – The male will immediately detect the pregnant females via sensing their hormonal changes. When that happens, the male will begin to chase the female and bump into it repeatedly, poking its sides and belly. This is to stimulate the female to release the eggs. You can’t miss this behavior since it’s not a typical interaction between males and females.
  • Inflated belly – You may not notice the signs of a pregnant female at first, but things will become clearer as the eggs grow. The female’s abdomen will grow larger by the day, especially towards the end of the pregnancy. Just make sure you eliminate other reasons for an inflated abdomen like constipation, dropsy, swim bladder disease, and others. You can do so by assessing whether there are other worrying signs accompanying the enlarged belly.
  • Changes in males – Interestingly enough, male goldfish will also display physical changes when getting ready to release their milt. Their gills and pectoral fins will showcase small white bumps that will go away soon after the breeding season.

These signs are pretty reliable indicators of upcoming spawning, giving you time to prepare the breeding tank.

How Long are Goldfish Pregnant?

There is no set time for goldfish pregnancy. This is atypical for the fish world, making for interesting behavior.

The female will carry the eggs as long as necessary until there are males around willing to fertilize them. Only then will the female goldfish release the eggs during a process that can last for several hours.

If a male never shows up, the female will eventually eliminate the eggs as unfit for fertilizing, but there’s no set time for that. It depends on the female’s age, environmental conditions, stress factors, etc.

You shouldn’t worry about it because the eggs will be released as long as you have male and female goldfish in the same habitat.

Your only worry should be what to do with the potentially thousands of eggs, resulting in hundreds of goldfish fry flooding the tank.

Where do Goldfish Lay their Eggs?

The female goldfish shows little consideration for the safety of its eggs. She will squirt them all over the place, typically on solid and fixed surfaces.

In a tank, the female will spread the eggs on plant leaves and roots, substrate, rocks, and other decorations nearby.

The eggs will stick to the environment since they’re coated in a sticky substance designed to keep them in place.

The female will not protect the eggs after spawning them, leaving them vulnerable to other adult fish. So, if you care about your goldfish fry, you better have a breeding tank ready.

How Often do Goldfish Lay Eggs?

Goldfish will produce eggs around 2-3 times per year if the environmental conditions allow it. They will mostly produce eggs in the spring and summer when temperatures are higher, and the food is plentiful.

If you want to mimic those conditions, provide your goldfish with higher water temperatures (around 68 F would be optimal) and high-protein meals.

These measures will put the goldfish into mating mood sooner, allowing you to breed them more often. Providing the goldfish with adequate conditions will also boost their fertility, allowing females to produce more eggs more often.

There have been reports of goldfish females laying more than 10,000 eggs over the course of several weeks.

You shouldn’t expect that many eggs, realistically speaking, but you can significantly increase your goldfish’s fertility by optimizing its diet and environmental conditions.

How Many Eggs do Goldfish Lay?

You should expect several hundred eggs during the breeding season. Of course, the number of eggs being produced depends on several factors, including the female’s genetic makeup, age, diet, temperature, and water conditions.

Goldfish are typically sexually mature at 1-year of age, but being sexually mature isn’t the same as being a prolific breeder.

Female goldfish will produce more eggs when they’re 3-years of age or older. Higher temperatures, stable water parameters, and a protein-rich diet will also influence the female’s fertility rates.

In a good season, you should expect your female goldfish to produce in excess of 1,000 eggs over the course of several days.

Is Goldfish Pregnant or Have Dropsy?

Learning the difference between pregnancy and dropsy is critical for obvious reasons. The most important one is that dropsy can be deadly under the right circumstances. Fortunately, it’s easy to differentiate between the 2.

Dropsy comes with additional symptoms compared to a normal pregnancy, including:

  • Bulging eyes
  • Pale and sometimes stringy feces
  • Swelling around the anus, which is always a sign of a health issue
  • Open scales, pointing outward rather than sticking to the body
  • Changes in appetite with goldfish even refusing food altogether
  • Visible lethargy and low levels of energy throughout the day
  • A curved spine

These symptoms have nothing in common with a normal pregnancy. The pregnant female goldfish will only display an inflated belly; other than that, its behavior should remain within the normal parameters.

If your goldfish displays dropsy-related symptoms, you need to act fast. This disease is notoriously difficult to combat, displaying rather low recovery rates.

The treatment should consist of quarantining the fish and providing a stable diet, pristine water parameters, and antibiotics if necessary. Melafix is a great option in this sense.

It’s worth noting that dropsy is most often the result of improper living conditions, mostly affecting fish living in dirty tanks and foul waters.

Provide your goldfish with an optimized, protein-rich diet and keep its water quality high, and you will eliminate the risk of contracting dropsy.

Conclusion

Goldfish aren’t as great breeders as livebearers like guppies, but they can come pretty close.

A female goldfish can produce thousands of offspring a year under the right circumstances.

If you’re planning to breed your goldfish, consider the following:

  • Prepare a breeding tank to prevent adults from eating the eggs or the fry
  • The fry will lay near the substrate and won’t eat anything for the first couple of days, so don’t feed them during this time
  • Remove unfertilized eggs to prevent them from rotting away in the water. Fertile eggs are transparent with a black dot inside, while unfertile eggs will remain white and turn darker over time
  • Provide the goldfish with higher temperatures and more protein during their mating season to stimulate and optimize the breeding process

Other than that, you only need to provide your goldfish with clean and stable water conditions, and they will do the rest.

avatar I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.

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