how to tell if an angelfish is a boy or girl

How To Tell The Difference in Male And Female Angelfish

Last Updated on: 11th October 2023, 04:04 pm

For saltwater species, the differences between males and females are subtle. Freshwater variants are near-impossible to distinguish since they have little sexual dimorphism.

Female angelfish are usually slightly smaller than their male counterparts. They’ll have smooth front fins, a lower dorsal fin, and a tube-like papilla.

Males are rounder in shape, with more erect dorsal fins, forked front fins, and a triangular papilla. Males will also have a noticeable bump on the forehead.

In marine angelfish, females may be duller in color and have fewer patterns.

It’s virtually impossible to sex juvenile angelfish. Physical differences aside, the most effective means of sexing an angelfish is allowing them to mature. They’ll pair off into breeding pairs or harems.

This will reveal their spawning behavior and the shape of the individual papilla.

How To Determine Male And Female Angelfish

Angelfish come in two main categories, each with different indicators of gender. These include:

  • Saltwater angelfish (marine angelfish). These come from the ocean waters in the southern hemisphere.
  • Freshwater angelfish. As the most popular type to keep in aquariums, these fish originate from rivers throughout South America.

There are over 100 species of angelfish – some marine, some freshwater.

Most share common traits in their appearance and aggression levels. However, all species display little sexual dimorphism. That’s the technical term for visual differences between male and female fish.

In general, males and females look almost entirely identical.

No matter the type, it’s impossible to tell males from females before maturity. You must wait 5 to 7 months from hatching before attempting to sex an angelfish.

Determining The Sex Of Marine Angelfish

Sexing a marine angelfish will be slightly easier. Once they’ve reached maturity:

  • The size differences will be more prominent.
  • The coloring and patterns may be duller in females.

However, this is usually only helpful to experienced aquarists.

You’ll need to know your particular species well. When you’re familiar with the average sizes and colors for a male or female, you can make an educated guess.

However, this information can still be muddled. The differences will be slight unless you have a male and female side-by-side to compare directly.

how to tell male and female angelfish apart

Male Vs. Female Freshwater Angelfish

Freshwater angelfish are the most popular type to keep in home aquariums. As such, it’s ironic that these are the most challenging fish to sex. Males and females will be nearly the same in:

  • Size.
  • Coloring.
  • Behavior outside of mating season.

Certain types will have more differences than others. If the species in your aquarium show no physical differences, you’ll have to wait until they start mating. This should give you one or two clues to follow.

How To Tell Male And Female Angelfish Apart

For the best sexing results, you need angelfish to compare. Ideally, you’ll have 6 or more angelfish in a single tank. Of course, the aquarium must be large enough to house them, or they may:

  • Begin fighting out of fear and constraints rather than sex-specific aggression.
  • Lack of exercise and food. This can impact their growth and make all your fish smaller or larger than their sex-specific size.
  • Trouble pairing up. With a space and food shortage, they’ll worry about surviving more than mating.
  • Lose coloring. Angelfish that are malnourished or stressed will become dull in color with fewer stripes. This can muddle your gendering tests.

If the tank conditions are perfect, you can then use each angelfish as a comparison for another. You should look for:

  • The size of their belly.
  • Their markings and patterns.
  • The intensity of their coloring.
  • Their aggression levels.
  • Any bumps on their head.
  • The shape of their dorsal fin.
  • Any forks in their ventral fins.

These will be their leading visual indicators. If you can’t tell any difference, then look a bit closer. It may not give you a firm answer, but it will better inform your guesses.


Males are often more colorful and patterned than female angelfish. In contrast, females bear duller coloring and reduced patterns. It is more common to see drastic dimorphism in marine than freshwater angelfish.

Bodies And Bumps

Across all angelfish species, males usually have a larger body and a notable bump on the forehead. Occasionally, this latter feature appears before maturity. Female angelfish will have a smoothly sloped dome without a bump.


In certain angelfish species, the dorsal fin may be more upright in females. It may slope down in males.

Male freshwater angelfish have ventral fins that are forked. Females do not. Keep in mind that this isn’t true for all species. Your type of angelfish may have no forks, regardless of gender.


Between these fins and the anal fin is the papilla. Male angelfish will have a thin, pointed vent. Meanwhile, females have a thin, tube-like vent with a rounded tip.

These are not always visible and may only appear when males and females are grouped. The traits become more prominent during the breeding season.

Belly Size

Take a long gander when the fish is looking directly at you. Female fish sometimes have a rounder belly to accommodate their eggs.

How To Tell If An Angelfish Is A Boy Or Girl

However, there are cases where all the physical traits are identical for every fish in your tank. Perhaps:

  • You’ve managed to purchase several fish of one gender.
  • You own a species that shows no physical differences.
  • Your fish have not adequately developed yet.

If that’s true, you’ll need more thorough examinations. Here are more accurate ways to parse the males from the females.

Waiting For Matured Fish To Pair Off

Angelfish typically pair off into male-female pairs at maturity. A close observation should reveal angelfish separating into these pairs.

The pairs may kiss, which is a popular trait in the species and signifies courting behavior. You can then be sure that one is male and the other female.

This method is only used for freshwater angelfish. Marine angelfish will group into harems of 1 male and multiple females instead of 1-1 pairs.

Marine angelfish are territorial, so having more than one in each aquarium isn’t advised. That is unless it is a species that mates for life.

If you own freshwater angelfish, then a pair is a valuable clue. Knowing that one is male and the other is female, you can tell them apart by their spawning behavior.

Observing Spawning Behavior

Angelfish are not live bearers, meaning that they reproduce through spawning. A female angelfish will lay her eggs directly onto a suitable surface using her tube-like vent. A male fish will then release sperm in a cloud over the eggs.

During spawning, the papilla of the fish will also be visible. However, it can be challenging to see the organs of smaller species. Instead, it’s best to observe which fish lays the eggs.

Sadly, this does rely on being in the right place at the right time. Both male and female angelfish will take turns fanning the fertilized eggs to keep them oxygenated.

This method does require you to cohabitate multiple angelfish in the aquarium. This isn’t an ideal method if you’re trying to create single-sex aquariums to prevent breeding.

The eggs can be removed if necessary, but the fry will hatch within days of the eggs being fertilized.

Are Male Angelfish Bigger Than Females?

The size of an angelfish will mostly depend on:

  • Its species.
  • The amount of food it eats.

However, if the conditions are ideal, the males may be larger than the females. These differences are usually slight, relying more on the body’s shape than the size.  

  • Males tend to be more circular.
  • Females are more angular.

Do Male Angelfish Grow Faster Than Females?

Male angelfish also tend to grow slightly faster than females. That’s helpful when you know all the angelfish in your tank are the same age.

You can look at which have grown more quickly and identify them as males.

However, some fish will be more territorial and claim more food. This can help it grow in size more rapidly. That will muddle any educated guesses at the creature’s sex.

determining the sex of angelfish

Are Male Angelfish More Aggressive Than Females?

Males are generally more aggressive than females. In freshwater angelfish, males often attack rivals and more vigorously defend their territory. This is designed to impress female angelfish into choosing them as mates.

Marine angelfish are even more prone to this. Males will chase other males away from their harems.

However, this information isn’t a great benchmark. That’s especially true during mating season. Females may grow just as aggressive and defensive of their:

  • Mates.
  • Fry.
  • Territory.

That’s because freshwater angelfish need a lot of space. Aquariums that lack space or are too crowded will see aggressive behavior. Likewise, angelfish that pair for life share the responsibility of their children.

Males and females can show the same aggression over their eggs and fry. Because of its protective habits, you can’t tell which one is the mother.

Can Angelfish Change Gender?

Certain kinds of fish can change gender. If your supposedly male fish starts mating like a female, you may conclude that it has changed its sex. This can be both true and false.

Marine angelfish can change from female to male. It’s rare to see this happen the other way around. Additionally, it’s only possible in certain species of marine angelfish.

Meanwhile, freshwater angelfish cannot change their sex at all. No matter the situation, these fish are stuck with their birth gender. If your fish starts manifesting signs of a different gender, then it hasn’t tapped into a biological trick. Your guess was simply incorrect.

How Do Angelfish Change Sex?

Sequential hermaphroditism is when animals spontaneously change from male to female or female to male. This is usually due to social or environmental factors.

Zoological Science notes that this phenomenon is common in reef fish species. That’s especially true for haremic social structures, which marine angelfish have.

Researchers discovered that the marine angelfish, called Centropyge ferrugata, could change sex.

Copeia notes four other species of marine angelfish that have presented protogynous hermaphroditism as well. These fish change on a physical and physiological level, adopting traits of the opposite sex, like:

  • Organs.
  • Reproductive abilities.
  • Physical appearance.
  • Behaviors.

Most commonly, marine angelfish experience protogynous hermaphroditism. This is a female-to-male change. It’s rare for males to transform into females.

Despite being in the same family, freshwater angelfish lack this trait. They cannot change their sex, even if it would help them environmentally or socially.

Do You Need To Sex Angelfish?

It’s vital to sex your angelfish if you intend on:

  • Breeding the fish.
  • Preventing any breeding habits.

This will allow you to pair them or separate them as needed. However, if you’re struggling to tell the gender of your angelfish, you can wait until they’ve started to form pairs. At this stage, you can separate one from the other:

  • In different tanks.
  • With a divider in one tank.

This will prevent breeding. The care and treatment of each fish will not change based on gender. You can keep multiple angelfish without ever knowing their sexes.

Your fish can live in harmony if you’re prepared to remove the eggs when they appear.