Difference Between Male and Female Goldfish

A lot of people love to have an aquarium at home full of colorful fish. The most common fishes which can be seen in the aquarium are Goldfishes. 

Have you ever thought of distinguishing between male and female goldfishes, although they are very similar? As they become mature, there can be seen certain differences between them.

Male Goldfish vs Female Goldfish 

The main difference between Male and Female goldfish is the Male goldfish are smaller and thinner in shape while females are bigger and rounder in shape. During the spawning season, the males undergo some changes like changes in pectoral fins and the development of tubercles. In contrast to that, Females develop swollen vents under the tails.

Male and Female Goldfish

Male goldfish are smaller and thinner in shape. They tend to be more aggressive than females. During the spawning season, male fishes tend to chase the female goldfish. The male females have certain body changes during this season. They develop the small little spots on the gills and pectoral fins.

Female goldfish are larger and round. They have quite timid behavior. During the spawning season, their vents under the tails become more open and swollen. They lay eggs in the breeding season. The female’s fin is rounder than shape, and also mid ridge line is absent in them.

Comparison Table Between Male and Female Goldfish

Parameters of ComparisonMale GoldfishFemale Goldfish
Body ShapeThe female goldfishes are more round and generally plump in shape.The male goldfishes have slender body shapes. They are longer and thinner than females.
FinsLocated just under and behind the gills, the pectoral fins are round in shape.The pectoral fins are longer and more pointed in shape.
BehaviorThe female goldfish is less aggressive and is quite timid.The male fishes are more aggressive and tend to chase the females.
VentsThe vents of a female fish are convex and round in shape.The male fishes’ vents are concave-shaped and thin.
TuberclesThe little spots or bumps don’t develop in females.During spawning, little white spots or bumps develop on mature male goldfish called tubercles.

What is Male Goldfish?

Male goldfish is the one that releases milt to fertilize. During spawning, male goldfish develop little white bumps on their heads and their pectoral fins. In this season, also the rays can be noticed on the pectoral or hind fins in males. The male goldfishes are longer and thinner than the females. They have longer and pointed pectoral fins located under and behind the gills. The vents, which are the anal opening of the fish, are thinner, concave, and indented in the males. Males have a mid ridgeline which is reduced or absent in females.

Once the breeding season starts, it is easier to find out the difference between males and females. The males tend to chase the females and thus become active in this season. They tend o be more aggressive than females.

What is Female Goldfish?

Female goldfishes are larger and rounder in shape and carry eggs. When they are mature, they are plumper, and their body seems to be more uneven than males. The females are quite timid. They are the ones who got chased and harassed by aggressive males for the fertilization of eggs.

The Pectoral fins located under the gills are rounder and less stiff than the males. During the breeding season, the females have certain differences in their body which can be seen. The anal opening called vents becomes larger, rounder, and stick out. The vents have two purposes, one is to release waste, and the second is it’s how they breed. The abdomen of the females is filled with eggs, and that makes their abdomen softer than the males. Their plump size increases during the breeding season. The mid ridge line is absent in females. 

Main Differences Between Male and Female Goldfish

  1. The first difference between Male goldfish and Female goldfish is their behavior. Male tends to be more aggressive and chase the females during the spawning season, whereas Female is quite timid in behavior and they are one being harassed by the male goldfishes.
  2. The Male goldfishes are longer and slender in shape, whereas the females are rounder, plumper, and larger in shape.
  3. The vent under the tail of females are convex and round in shape, whereas Males have concave-shaped and are thin. The vents in females become rounder and puffed to breed. Males tend to release milts, whereas Females tend to release waste and eggs.
  4. Males have their pectoral fins longer and pointed in shape, whereas Females have pectoral fins of round and short in shape. Also, the little white bumps appear in the heads and pectoral fins during the breeding season in males, not in females.
  5. During spawning season, small bumps develop on the heads or the gills in male goldfishes, whereas these little bumps along with the mid ridge line are absent in females. The abdomen, which carries eggs, becomes softer in females than the males.


The difference between the male and female goldfishes is difficult to understand when they are young. Once they start getting mature, one can observe the visible changes in them. Whether it is their behavior, their body shape, or the shape of fins, they all change.

 Male fishes tend to be more active in the breeding season. They both go with certain changes in the spawning season. Knowing the sex of the goldfish is important for the breeding purpose as well as if one wants to name them. Moreover, Males release milts, whereas females release eggs. Certain changes can be seen in the breeding season.

Taking into account the differences given, one can easily decide which is male and which is female goldfish.


  1. https://www.sciencedirect.com/science/article/pii/0018506X89900469
  2. https://www.sciencedirect.com/science/article/pii/S0045653519300335
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