Can Goldfish Change Gender?

Have you ever wondered if your goldfish is able to change gender? Many fish can do just that. Maybe you’ve even heard that goldfish can, too.

So, can goldfish change gender? As cool as that would be, they can’t. Goldfish are either male or female. But don’t worry, it’s not that hard to tell them apart.

Can Goldfish Change Gender?

The answer is “no”. Goldfish cannot change gender, they will always be either male or female. But, why might you need to know this?

Perhaps you’d like to breed your goldfish. Well, then you’d need to know how to tell the sexes apart. Or, on the flip side, maybe you’re trying to avoid your goldfish breeding. Then, you may want to get all males or all females.

Lucky for you, it’s not that difficult to tell the sex of a goldfish.

How Do You Tell Male From Female?

Male and female goldfish look very similar at first glance. But, if you take the time to look, it’s really not hard to tell them apart.


Female goldfish tend to have larger, rounder bellies than their male counterparts. This is true any time of the year, but their belly is especially pronounced while they’re pregnant. When they are pregnant, a female’s sides will begin to bulge where the eggs are growing. This may make her body look less symmetrical.

Conversely, a male’s body is generally more streamlined and thinner. A female’s body also tends to be bigger than a male of the same age.

During the breeding season, a female’s anal ventricle becomes swollen. It will look like it’s protruding slightly from the body. Males have anal ventricles as well, but they won’t protrude.

Unlike many animal species, the females tend to be more brightly colored than the males.

Females also swim faster than males.


If you’re still unsure how to tell them apart, don’t worry. It’s a bit easier to distinguish the males than the females.

Take a look at their pectoral fins — the fins on the sides of their body. The male’s pectoral fins are longer and thicker than a female’s. They will also appear more jagged. You can also take a look at their tail fins. A male’s tail fin is usually longer and more pointed.

Next, take a look at their gills. Males may have raised bumps residing on their gill covers. These bumps are “breeding tubercules”, and they are white in color. This is not a surefire way to tell if your fish is male, though. The tubercules only appear when the male is ready to mate.

If you’re able to get a peek at their belly, see if you notice a line. The males have a raised line that runs along their belly that is missing in the females.

Breeding Patterns

If you’re still not sure how to tell them apart, take a look at their behaviors during the breeding season. Females tend to be calm and will hide amongst rocks and plants. They will sometimes stop eating as well.

Females are also faster swimmers than males. They sometimes need to use this to their advantage.

The males will chase females around the tank when they’re ready to breed. Oftentimes, they can become quite aggressive about it.

But, once they are pregnant, the females become quite slow.


While goldfish cannot change genders, it’s pretty easy to tell males and females apart. The females tend to have larger bellies. Plus, their anal ventricles will protrude slightly. So, if you were wondering whether your goldfish was male or female, now you have a way to find out!

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