Pea Puffer Male vs Female – How to Tell the Difference?

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Pea Puffers garner a lot of attention thanks to their distinguishable look. This fish remains unmistakable due to its tiny size, signature yellow coloration, and puffy body.

You know what you’re looking at when you see a Pea Puffer. Or do you?

While this quirky-looking species is easy to differentiate from other fish, telling apart male and female puffers is a different story.

You might find it troublesome when you want to breed or separate your puffers in different tanks, but you can’t tell the males and females apart.

If that’s the case for you, keep reading! In this article, I’ll go over the subtle yet very important differences between male and female Pea Puffers.

By the end of the article, you should be able to sex your fish without trouble.

How to Tell if Pea Puffer is Male or Female?

At first glance, one Pea Puffer looks like any other you’ve seen before. These fish are yellow, up to 1.5 inches long, and have a round body shape and big, googly eyes.

But look closer, and you’ll notice subtle differences between male and female fish.

Here are some of the signs to look out for to sex your Puffers more effectively:

– Body Size

Pea Puffers are very small. They’re generally shorter than 1 inch long, but some might grow up to 1.5 inches.

This range leaves some room for variation in body size. And this variation is most apparent between males and females.

Take a closer look at your fish, and you might notice that some appear longer and “taller” than others. Female Puffers are usually slightly larger than males.

This distinction applies to over 80% of all fish species, as females tend to be larger than males on average.

– Body Shape

Pea Puffers have a stout build. Both sexes have full, puffy-looking bodies. However, there are still slight differences in body shape.

Males will appear slightly more elongated and “thinner,” if you can call them that.

Females have rounder bellies and look slightly wider when seen from above. A female’s tail might also appear shorter due to body volume distribution.

Female Pea Puffers have a nearly oval body shape when seen from the side, while males appear round, with an extended tail.

– Coloration

Male and female Pea Puffers are yellow, but if you look closer, you’ll notice differences in shade and hue.

Males have rich golden-colored bodies and dark green patches. Females, on the other hand, have lighter, more muted colors.

Patterns on the body also differ. Male Puffers have a dark stripe stretching vertically across their bellies.

Females have no stripe. But they have dark freckles between the large splotches across their backs.

– Behavior

Pea Puffers as a species are feisty and aggressive. They have big, fiery personalities, despite their deceptively cute appearance.

But their tendency towards aggression will vary, with males being more violent than females.

Male Pea Puffers are particularly territorial and hostile to other species and other male Puffers. Female Puffers are less likely to chase or attack other fish unprovoked.

Puffers are friendly and peaceful to each other when there are more females than males in the school.

– “Eye Wrinkle”

This is another telling physical characteristic, and it only exists in males. Male Pea Puffers have a light, iridescent pattern surrounding the eye.

These lines look like cracks, so most people refer to them as “eye wrinkles.” This pattern doesn’t exist in females.

At What Age Can You Sex Pea Puffers?

A Pea Puffer’s distinguishing traits don’t appear until the fish are fully developed. In other words, you must wait until your Puffers are mature enough to breed.

Most Pea Puffers reach maturity 7-8 months after hatching. Until then, any attempt to sex your Puffers is just a guessing game.

Trying to sex your Puffers before this point will only make things more confusing. During the juvenile stages, all the fish appear female.

However, they don’t yet have a sex. Pea Puffers choose their sex during the later growth stages.

And they do so according to environmental cues. Separating your Puffers early on might influence their development in unexpected ways.

Can Pea Puffer Change Gender?

Pea Puffers are unique because they aren’t born with a gender. Instead, they “choose” their gender during the later stages of development, when they turn from juveniles to adults.

But no, they aren’t changing their gender as one would typically think.

You could say that when they hatch, all Puffers are “neuter,” for lack of a better word. Environmental factors like nutrition, the number of other fish in the tank, and the forming of social hierarchies will influence how the Puffers mature.

So, Puffers go from no gender to either male or female. This only happens once during their lifetime.

Typically, the most dominant fish in the group will become male. Once the male starts developing, it secretes hormones in the water that inhibit other Puffers from becoming male.

Sometimes, you can get two males in a group, but one of them will be a subdominant male.

Once the Puffers have matured into either males or females, they can’t change their sex. Some female fish might take on a dominant role if you remove male Puffers from the tank.

But they won’t be able to reproduce with other females. Subdominant males also often get mistaken for females due to their duller coloration.

If it seems like two female Puffers managed to breed, you have a subdominant male in the tank.


Pea Puffers have a unique look that makes them easily distinguishable from other species.

At first glance, males and females look very similar. However, there are a few traits to look for when sexing your fish. Things to consider include size, body shape, coloration, and behavior.

Females are larger and rounder, while males have brighter colors. Other distinguishing traits in males are the dark line on their bellies and their iridescent “eye wrinkles.”

Males are also more aggressive and territorial than females.

Always remember to wait 7-8 months before sexing your fish. Pea Puffers are born without a biological sex.

They only “choose” their sex during the later stages of growth. Sexing your fish before they become adults would be impossible because of this.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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