Male or female goldfish? How to tell (with pictures)

The easiest way to tell if a goldfish is male or female is during the spawning season. In the wild, this is spring and summer, although it can be any time of the year in a home aquarium.

During spawning, male goldfish develop spots on their gills and pectoral fins. Whereas female goldfish will have a swollen hole under their tail.

The fish will also behave differently: male goldfish will chase females much more often than usual.

By looking out for each of these clues during spawning season, you can figure out which of your goldfish are males and which are females.

Male goldfish:

  • Have spots on the gills
  • They have spots on their pectoral fins.
  • Chase women
  • Release milk to fertilize eggs

female goldfish

  • Have a vent that clumps out
  • Chase men
  • lay eggs

Let’s look at some photos of male and female goldfish so you know what to look out for.

How the hole tells you if a goldfish is male or female

In goldfish, the vent serves two purposes. This is how they excrete waste and this is how they reproduce.

The females release the eggs through the hole, while the males release milk, which fertilizes the eggs.

The vent hole in male goldfish is flat and not very noticeable. It’s just a small gap hidden under their tails.

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In female goldfish during the breeding season, the anus swells and protrudes.

The difference can be seen in the photos below, from Bristol Society of Aquarists.

Above: The opening of a male goldfish. (There’s nothing to see here!)
Protruding hole of a female goldfish
Above: Hole of a female goldfish. Notice how it sticks together.

Identification of reproductive tubercles in male goldfish

Male goldfish develop small white bumps on their gill covers called breeding tubercles.

Goldfish with gill spots
Notice the spots on the gills of the goldfish and around the eyes.

Spots or “stars” usually also appear on the pectoral fin of the fish, as you can see in the photos below.

Close-up of goldfish breeding grounds on gills
Another view showing proliferating tubercles on the gills, pectoral fin and around the eyes.

What are breeding tubercles for?

It is not entirely clear why the tubercles are actually needed for the reproduction of goldfish. However, scientific evidence suggests that they help show that male goldfish are in a healthy state to breed.

Male goldfish with more breeding tubercles tend to be healthier and more successful in breeding.

Thus, bumps may be an outward sign to female goldfish that the male is a good mate choice.

How to tell breeding stars from their parasite

White proliferating bumps can easily be mistaken for white spot disease, also known as Ick or Ich.

You must ensure that the spawning season is in progress before attempting to treat any disease. Improper treatment of the disease can lead to a violation of the timing of spawning and the improvement of the aquarium or pond.

Breeding stars look like small dots with a very neat, regular pattern. They are also most commonly found on the gills and pectoral fins (although they can be found anywhere on goldfish).

Ich produces similar-looking white spots, but the spots tend to vary in size and appear without an organized pattern. They also spawn randomly throughout the fish.

Chasing behavior during spawning

During spawning, male goldfish chase females and beat them against the walls of the aquarium.

Orange and white male and female goldfish swimming together
Typical mating behavior of goldfish. The male is chasing the female.

Watching one goldfish chase another gives you an idea of ​​whether it is male or female.

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The chase suggests that the fish is male. During the chase, it can be assumed that the goldfish is a female.

However, this is not always a reliable system. Especially if you keep goldfish of different ages in the same aquarium.

Sometimes, when fish release pheromones during spawning, immature young fish begin to behave inappropriately for their sex.

You might think you have a female because she’s being chased, but then the next year she’s got breeding bumps and you realize she’s a male.

Chasing must always be combined with other signs (such as the reproduction of tubercles or the release of eggs or milt) to accurately determine whether a goldfish is male or female.

Release of caviar and milk: the easiest way to determine whether a male or female goldfish

Of course, the easiest way to tell if a goldfish is male or female is to notice how they release milk or eggs.

Obviously, if you see a goldfish laying eggs, then you know it’s a female. And if you see how a goldfish releases milk, then know that this is a male.

But what does it look like?

Here are some pictures to help.

Male goldfish release milk
See the white lines in this picture that look like wisps of smoke? This is the milk coming out of the anus of the male goldfish.

How old do goldfish have to be to tell if they are male or female?

The physical differences between male and female goldfish will only become apparent once the fish have reached sexual maturity and are in good health.

The normal age for goldfish to reach maturity is over one year old. However, sometimes the fish may reach maturity sooner or later.

If you’re trying to breed goldfish, it’s best to shop for six goldfish from one tank because you have a high chance of getting a male and a female.

Just make sure you have a large enough aquarium or pond to accommodate them all safely.

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Other physical characteristics of male and female goldfish

The main signs of male and female golden color:

  • Spots on gills and pectoral fins during breeding season (males)
  • Vent hole that sticks out (women)
  • Stalking (males) and stalking (females)
  • Egg laying (females) and milk production (males)

More subtle and less reliable secondary features include:

  • The pectoral fin of male goldfish is thicker and longer.
  • The pectoral fins of males are usually more pointed than those of females.
  • The anal fin in males is closer to the tail than in females.
  • Male goldfish have smoother fins and tails than females.
  • Male goldfish tend to have a slightly smaller and leaner body compared to females.
  • Females will have a larger and rounder body, and their belly may appear soft.
  • Females may be asymmetrical during the spawning season when viewed from above due to the development of eggs.
  • Often females have a deeper body compared to males when viewed from the side.
  • The ridge that runs across the back of the pelvic fins to the opening of the anus is often more pronounced in males and less or absent in females.

However, these secondary rules are not true for all goldfish. Therefore, we recommend that you do not draw any firm conclusions about whether a goldfish is male or female until you have found some of the basic signs.

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