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How to Tell if a Goldfish Is Male or Female?

Goldfish are freshwater fish in the family Cyprinidae of the order Cypriniformes. They are one of the most commonly kept aquarium fish. A relatively small member of the carp family, the goldfish is a domesticated …

Identification of a male or a female goldfish

Goldfish are freshwater fish in the family Cyprinidae of the order Cypriniformes. They are one of the most commonly kept aquarium fish. A relatively small member of the carp family, the goldfish is a domesticated version of a wild carp native to East Asia.

In this article, you will learn how to tell if a goldfish is male or female. You will also learn how to breed goldfish.

How to Identify Goldfish Gender?
To determine the sex of a goldfish, look at the fish’s vent, which is located between the anal fin and the tail fin. The vent of a male goldfish is round and protrudes, while the vent of a female goldfish is more oval-shaped and lies close to the body. Additionally, male goldfish tend to have longer fins than female goldfish.

Female goldfish

  • Lay eggs
  • Get chased by males
  • The abdomen is oval

Male goldfish

  • Have spots on their gills
  • Release milt to fertilize eggs
  • Have spots on their pectoral fins
  • The abdomen is round and protrudes

Goldfish Male or Female Pictures

Identifying a male or female goldfish

Is There a Trick to Successfully Sexing Goldfish?

Goldfish can be bred by following a few simple steps. Breeders will need a tank, some plants, and a few goldfish. The tank should be at least 20 gallons and have a filter. The plants will provide cover for the eggs and the fry. The goldfish should be fed a quality diet to ensure healthy eggs and fry.

To breed the goldfish, the male and female should be placed in the tank together. The male will start to chase the female, and the two will eventually spawn. The eggs will be scattered among the plants and will hatch in a few days. The fry will need to be fed a quality diet, such as baby brine shrimp, to ensure they grow healthy and strong.

How to Tell the Sex of a Goldfish?

Let’s go into more detail on how do you know if a goldfish is a boy or a girl.

1. Watch for behavior

Male and female goldfish can be distinguished by their behavior. Males are generally more active and aggressive, while females are more passive. Males also tend to chase other fish, including females.

When two goldfish are placed together in a tank, the male will often chase and bump into the female. If the female is not interested in breeding, she will swim away from the male. If the female is ready to breed, she will allow the male to chase her.

2. Check the Vent

If you’re wondering how to tell if a goldfish’s gender is female or male, one of the easiest ways is to look at the vent. The vent is located just behind the anal fin, and in males, it will be slightly protruding and have a small white bump on it. Females, on the other hand, will have a vent that is flush with the body and doesn’t have a protrusion or white bump.

3. Breeding stars

The easiest way to distinguish breeding stars in male and female goldfish is to look at the fish’s vent, which is located just behind the base of the tail.

The female’s vent will be rounder and more prominent, while the male’s vent will be narrower and less noticeable.

4. Body shape

There are a few key differences in the body shape of male and female goldfish that can help you to identify the sex of your fish. Firstly, male goldfish tend to be slimmer than females and have longer and thinner tails. Secondly, a male goldfish’s vent (the opening through which they excrete waste) is usually longer and thinner than a female’s.

Finally, and perhaps most importantly, male goldfish also tend to have a small bump on the leading edge of their pectoral fins (the fins located on either side of their body just behind the head). This bump is called the gonopodium and is used by the male to transfer sperm to the female during breeding. If you cannot see this bump, your goldfish will likely be female.

5. Fin shape

So, how to tell the sex of a goldfish by the shape of the fin? Generally, male goldfish will have longer and thinner fins than their female counterparts. The fins of a male goldfish will also be more pointed, while the fins of a female goldfish will be more rounded.

6. Spawning

How to goldfish gender identification by Spawning? It is not easy to determine the sex of goldfish by spawning. The easiest way is to wait until the fish are ready to spawn and then look for the genital papilla in front of the anal fin on the underside of the fish. The female has a rounder genital papilla, while the males is more pointy. However, this method is not 100% accurate.

FAQs on Goldfish Gender Identification

How Old do Goldfish Need to be to Tell if They are Male or Female?

There is no definitive answer to this question as it can vary depending on the type of goldfish. However, generally speaking, goldfish need to be around 6-12 months old before you can accurately tell if they are male or female. This is because the sex organs of goldfish do not fully develop until they reach this age.

At What Age Do Goldfish Start Breeding?

Goldfish reach sexual maturity anywhere from four to 36 months, depending on the species. For most goldfish kept as pets, sexual maturity occurs around 12 to 18 months of age. The timing of sexual maturity also depends on the size of the fish; smaller goldfish tend to mature sooner than larger goldfish.

How Do Goldfish Breed?

Goldfish reproduce by laying eggs. The female goldfish will lay thousands of eggs at a time, and the male goldfish will fertilize them. The eggs will hatch in about two weeks, and the fry will be able to fend for themselves.

What Kind Of Breeding Technologies Exist For Goldfish?

Many breeding technologies exist for goldfish. Some of these technologies include inbreeding, outbreeding, and selective breeding.

Also read:


In the article, you learned about the male and female goldfish differences. Overall, there are a few ways that you can determine the sex of a goldfish. One way is to look at the fish’s belly. If the belly is round, the fish is most likely a female. If the belly is pointed, the fish is most likely a male.

Another way to determine the sex of a goldfish is to look at the fish’s fins. Male goldfish tend to have longer and thicker fins than females.


  • Brine shrimp (by The Editors of Encyclopaedia Britannica, Sep 21, 2022): https://www.britannica.com/animal/brine-shrimp
  • Gonopodium (Uit Wikipedia, de vrije encyclopedie): https://www.wikiwand.com/nl/Gonopodium

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