April 22

Getting Smart With Identifying Between A Male And A Female Goldfish

It’s understandable as an aspiring aquarist to know the gender of your pet goldfish either for breeding purposes or when it comes to naming them. Do you really want to be calling your female goldfish “George”?

Additionally, fish keepers need to know the gender of the fish if they are trying to set up a single-sex population.

Meantime, AquaPlanets has this video on Youtube that shows you 5 Ways To Identify Male Or Female Goldfish.

Let’s continue. This article will cover a detailed walkthrough on identifying if a goldfish is male or female by noticing specific physical characteristics and behavior signs.

The Difficulties You May Encounter

goldfish swimming

It’s true that gender identification isn’t as easy as ABC, and there is no foolproof method for sexing goldfish. Many factors like species, physical characteristics, and behavioral cues come into play.

Sometimes, the goldfish forgo reproductive functions to survive if they haven’t been provided with appropriate nutrition, space, or clean water. In this situation, since it is unlikely a fish will show external signs of gender differentiation, you are then left with observing their behavior during the spawning season.

For instance, some male goldfish may not develop tubercles while some female fish might. Additionally, male goldfish may have protruding vents, unlike a female goldfish. Species also play a factor.

For instance, goldfish breeds such as ranchu or ryukin naturally have thick and round body shapes, making it sometimes impossible to differentiate between males or females correctly.

Another way to tell if a goldfish is a male or female depends on the fish’s age. Since gender differences are easily identifiable once the goldfish reach maturity, some male goldfish will reach maturity when nine months old.

At the same time, it might take three years for a female goldfish to fully mature.

Other difficulties may also include a goldfish’s general health. Goldfish usually do not follow typical spawning behavior if deprived of quality water and appropriate nutrition.

For instance, an unhealthy male goldfish may not develop tubercles, or a thinner, underfed female goldfish may be misidentified as a male goldfish. Hence, when it comes to sexing goldfish, it is best not to rely on only one sign.

Get your Goldfish Stuff at Amazon

Photo Title Price Buy
Mini Encyclopedia of...image Mini Encyclopedia of Goldfish: Expert Practical Guidance on Keeping Goldfish Plus Detailed Profiles of All the Major Varieties $13.19
Tetra TetraFin Goldfish...image Tetra TetraFin Goldfish Flakes 4.52 Pound Bucket, Balanced Diet $44.60
Goldfish Aquarium Goldfish Aquarium $19.99
Fancy Goldfish: Complete...image Fancy Goldfish: Complete Guide To Care And Collecting $59.27

Five Ways of Sexing Goldfish

three goldfish swimming

Before identifying specific characteristics when sexing goldfish, you must know that goldfish are not sexually dimorphic until they reach adulthood. Dimorphism means physical characteristics to differentiate between the male and female sexes. 

    Sexually maturity of a typical goldfish lies between 9-12 months of age. At the same time, goldfish found at the pet store are usually 2-3 months old.

    So, chances are, you won’t know their sex until sexual maturity is reached. Additionally, sexing goldfish is done easily during the breeding season due to pronounced changes.

    Now, let’s dive into how you can tell if a goldfish is a male or a female.

    1. Protruding Vents

      Goldfish have a vent (anal opening), an opening on their body that releases genetic material like eggs or sperm and waste. Female goldfish have a slightly protruding vent, meaning if viewed sideways, the vent may appear to be outwards.

      Whereas, in male goldfish, the vent is inward or flat. Only during the breeding season will the vent in a male goldfish raise slightly, which only a wary eye can notice.

      Another way of identification is by looking for a midline ridge. If it is possible, you can also look at the underbelly of the fish, where you will notice a raised line running from the vent to the back of the pelvic fin; chances are it is a male goldfish.

    2. Behavioral Cues

      Goldfish’s behavioral cues may make it easier to differentiate between a male goldfish and a female one. For instance, male goldfish will often chase a female goldfish and nip at her back to stimulate her for eggs release.

      Sometimes, a male fish may chase multiple female goldfish, and numerous males may chase a single female goldfish. However, if you spot multiple males chasing a single female fish or tearing its fins, that’s a case of dealing with a bully, which must be dealt with by isolating the fish. Also, you must know that all goldfish interbreed. So, you can always add a divider to your aquarium if you want a pure strain of goldfish.

    3. Changing Body Shape

      When female goldfish are ready to spawn during the breeding season, they will plump up and develop around the abdomen to produce eggs. Sometimes the swelling is asymmetrical, meaning more bulging is shown on one side than the other.

      However, male goldfish generally have a streamlined and thin body shape that does not change when breeding. And will also develop light-colored, small bumps on their pictorial fins.

    4. Signs of Tubercles (Breeding Stars)

      One can spot visible differences in the pectoral fins of a male and female goldfish. For instance, in male goldfish, small white spots called tubercles may appear on their gill shields, on the scale of the body, and on the face.

      In males, breeding tubercles will only last during the breeding period. Males also have narrower and longer fins as compared to females.

      However, it’s important to note that not all males will develop tubercles which may lead to misidentifying the gender of your fish.

    5. Shape and Size of Fins

      The pectoral fins in male goldfish are longer, thinner, and pointed. However, female goldfish have shorter fins.

      Therefore, this identification method may not work if your goldfish species differ. For instance, veiltail goldfish genetically have longer fins.

      Also important to note that male goldfish generally have more flowing fins than females.


    Identifying the sex of your goldfish is indeed not as straightforward as it seems. It takes time, skill, and patience to be able to pick up on behavioral cues and physical characteristics in goldfish.

    Additionally, it also takes practice to hold your goldfish still and long enough to examine vents, fins, midline ridges, and body shape. However, understanding sexual dimorphism and spawning behavior may make it easier for fish keepers and aspiring aquarists to tell if a goldfish is a male or female.

    Lastly, goldfish breed in warm water. Therefore, to reflect changes in season, you must alter your aquarium’s water temperature, or your goldfish may end up breeding or interbreeding all year round.

    Commonly Asked Questions

    Here are a few commonly asked questions people have when keeping goldfish or breeding them. Going through them will make things more straightforward when it comes to sexing goldfish or any peculiar behavior they may have.

    How long does a goldfish live on average?

    ANS:  Unfortunately, most do not know this, but goldfish can live up to 10-15 years. Some species may also live up to 30 years.

    However, goldfish need adequate space to swim, proper care, and nutrition to live long and not fall prey to depression and stress.

    Do goldfish ever fight?

    ANS: Goldfish are generally calm and friendly fish. However, on rare occasions, if you spot any fights between your goldfish, it is better to put a divider in the tank or get separate tanks before integrating them again.

    What is the purpose of breeding tubercles?

    ANS: As the name suggests, breeding tubercles functions include species recognition, spawning, and breeding of females.

    How to differentiate between breeding stars and ich parasites?

    ANS: Breeding stars are small white dots formed neatly in regular patterns on the fish’s pectoral fin or face. They are often formed right before the breeding season.

    However, the white spot disease ich/ick so not form regular patterns and may vary in size. Before treating any disease, check in with your local veterinarian to avoid disruption in the goldfish’s health.

    How old does my goldfish need to be to tell if they are males or females?

    ANS: Apart from the physical differences that are visible between the two sexes. A goldfish must have reached sexual maturity and should generally be older than a year for one to tell if they are a male or a female.

    However, some goldfish species may show visible physical characteristics when they reach 2-3 years.

    Why is my goldfish sitting at the bottom of the tank?

    ANS: This is a common query among people, and the answer is not as simple. Goldfish are generally hyperactive and are always on and about doing something.

    So, it makes sense if you see a relatively inactive goldfish hanging at the bottom of your tank. And the reasons may or may not be related to health problems.

    Generally, if one spots goldfish at the bottom of the tank, it could be because the fish isn’t feeling too well. Either improper water conditions, lack of proper nutrition, stress, parasite, or bladder problems can all be reasons for your fish looking sad and isolated.

    It is best to pay a visit to your local vet if this behavior is prolonged.


    common goldfish, difference between male and female goldfish, female goldfish, goldfish female or male, male goldfish, physical characteristics of a goldfish

    You may also like

    Easy-to-Keep 10 Best Tropical Fish For Beginners

    Easy-to-Keep 10 Best Tropical Fish For Beginners

    The 10 Best Pet Fish Species For Kids

    The 10 Best Pet Fish Species For Kids
    {"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}