Since entering the aquarium hobby and peeling back the layers of discovery, I have been amazed by so many unique creatures and their strange worlds.

Clownfish, to my pleasant surprise rank towards the top of the list of unique sea creatures.

One of the strangest things they do is change from male to female if they are the most dominant member of a group of clownfish.

When I talk to people about this they often ask me if a clownfish can change from a female back into a male…

All clownfish are born male with male and female reproductive organs, but the biggest clownfish dominates which triggers hormones that cause his female reproductive organs to fully develop making him female, and then she can never turn male again.

Wow! I know right? That’s what I said.

I know this is crazy to us humans so let me explain…

Why Can’t a Clownfish Change From a Female Back to a Male?

Mammals are born with chromosomes that make their brain produce hormones that determine if they are a male or female at birth.

Clownfish are unique in that they are not born with these same chromosomes but they are born with male and female sexual organs.

They are born with chromosomes that are like sensors that can cause different mixtures of hormones in their brain which then determine what sex they are going to be at a certain point in time by determining the mixture of hormones in their brain.

Hormones are best described by https://medlineplus.gov/:

Hormones are your body’s chemical messengers. They travel in your bloodstream to tissues or organs. They work slowly, over time, and affect many different processes, including:

Growth and development

Metabolism – how your body gets energy from the foods you eat

Sexual function

Reproduction

Mood

Endocrine glands, which are special groups of cells, make hormones. The major endocrine glands are the pituitary, pineal, thymus, thyroid, adrenal glands, and pancreas. In addition, men produce hormones in their testes and women produce them in their ovaries.

Hormones are powerful. It takes only a tiny amount to cause big changes in cells or even your whole body.

Female Clownfish

The easiest way to explain this is to start at the top of the hierarchy.

All clownfish are born male but the most dominant clownfish in a group or pair, which is usually the biggest shows dominance or even bullies the rest of the clownfish.

This top dominance triggers a different mixture of hormones in the brain of the clownfish which causes his female sexual organs to fully develop, so now we can call him a her.

Once a clownfish develops into a female they are the most dominant member of the group and can’t change back into a male.

Really there is no reason to change back since only one female is needed to give birth.

The only reason for another female is if she days which leads us to the next member of the hierarchy…

Most Dominant Male Clownfish

Once the female becomes the female, her only partner can be the next most dominant clownfish which is still male, but the relationship of the group creates another unique mixture of hormones in the dominant male’s brain which cause his male reproductive organs to fully develop.

The most dominant male is usually the next biggest clownfish in size to the female.

Once the clownfish becomes the dominant male, he can not go back to being the juvenile that he was before his male sexual organs fully developed.

The only sexual change he can go through now is to become the female if she dies.

If the female dies, the social relationship between the dominant male and the rest of the clownfish creates the same mixture of hormones in his brain as the female had before she changed into a female.

So, what happens to the rest of the clownfish in the group?…

Juvenile Clownfish

Juvenile clownfish in the group are constantly dominated by the female and the most dominant male.

This domination actually keeps their size smaller and keeps their hormones suppressed so they can never develop their sexual reproductive organs unless the female or male dies.

Domination is the key to movement in the clownfish hierarchy but the juveniles will always remain the same unless the death of the dominant male or female causes one of them to become more dominant thus triggering the different hormone blend in their brain.

Unfortunately, some clownfish are destined to live their lives in the juvenile state, but it is not so tragic in the sense that they do not realize this.

Will a Lone Clownfish Become Female?

Since you are now educated in the fundamentals of clownfish hormones and what triggers them you may be able to guess this one yourself.

Come on you can do it…

Okay, I’ll tell you…

Juvenile clownfish’s hormones are suppressed by the dominance of the female and dominant male in the group.

When the juvenile is by themselves, such as in an aquarium, their hormones aren’t suppressed by the social interactions of a clownfish group so they become female.

In a sense, you could say they are the dominating clownfish in their tank since there is no competition.

How Long Does it Take a Clownfish to Turn Female?

Once the clownfish’s brain initiates the proper mix of hormones in their brain it only takes 3-4 weeks to become a female.

Remember, they become the dominant member of their group by being the biggest or else being by themselves which in a sense makes them the biggest till.

How Do You Know if a Clownfish is a Female or a Male?

The easiest way to tell if a clownfish is female is if they are the biggest in a group.

Of course, if they are by themselves, they are the biggest in the group so if they aren’t a female yet, they will be within a few weeks.

If the clownfish are close to size then the clownfish that dominates the others is the female.

As far as markings, there are some species of clownfish that have physical differences between males and females.

Maroon/Tomato Clownfish

The male is usually less than half the length of the female so it is obvious.

The male is also has a brighter color.

Clark’s Clownfish

The female usually has a white caudal fin and the males have a yellow caudal fin. The female may still have a yellow caudal fin but only if she is very young.

Pink Skunk Clowns

The tail fin of a male has a pink border.

Conclusion

Juvenile -> Male -> Female. Just remember this hierarchy and how it influences the hormones in the brain of the clownfish which then changes how much their male or female genitalia develop.

I hope we have completely explained that clownfish can not turn from female back to male, why, and the science behind it.

If you enjoyed our article, please checkout the rest of our clownfish section.