How to tell betta fish gender?

In this article we will discuss the ways to differentiate between male and female bettas.We will also learn about sexual dimorphism and colour changes in bettas.


In this blog

  • How to tell betta fish gender?
  • Betta fish general information 
  • What is sexual dimorphism?
  • Betta fish gender differentiation
  • Why do bettas change their colors?
  • Summary
  • Frequently asked questions
  • Reference

How to tell betta fish gender?

It is very easy to differentiate gender or sexes in betta fish.Gender differentiation is more prominent when they mature.In young or juvenile bettas differentiation won’t be prominent.

  • Size of bettas
  • Weight of bettas
  • Color of bettas
  • Body markings in bettas
  • Behavioral traits of bettas
  • Cognitive traits of bettas

Betta fish general information 

Bettas come from Southeast Asia, especially Thailand.They are considered as the national aquatic animal of Thailand.

Bettas are very beautiful fish and are known for their long attractive finnage and vivid color patterns.They have a very small life span of 3-4 years due to their poor genetics.

They are very sensitive to poor water conditions.They do well in spacious tanks with good oxygen circulation.Bettas need good and nutritious diet to maintain their finnage colouration and longevity. Overall a good beginner fish for new betta enthusiasts.

Bettas are unfortunately listed under the endangered category by IUCN because of human exploitation.Their natural habitats are being cleared for establishing oil palm cultivation.

What is sexual dimorphism?

Sexual dimorphism also known as sexual differentiaion, is a condition where the sexes of similar species exhibit different attributes apart from sexual characteirtics.The different secondary sexual attributes are:

  • Size of the species
  • Weight of the species
  • Color of the species
  • Body markings 
  • Behavioral traits of species
  • Cognitive traits of species.

Betta fish gender differentiation

Egg spotBody colorBody stripesBody shapeGills sizeFinnage pattern and tailsBeards size and visibilityFlaring patternsBehavior and aggressionBubble nest formationParental care

Egg spot in female bettas

  • The first and the most important way to differentiate the genders in bettas are by looking at the egg spots.
  • Egg spots are nothing but a small, white spot by the anus or more specifically between their ventral and anal fins.
  • The egg spots look like a grain of salt.
  • Female bettas are known to have to have egg spots on their body,while male bettas don’t have an egg spot on their bodies.
  • Only mature female bettas will have an egg spot by the anus on them.
  • Juvenile bettas won’t show egg spots on their bodies.
  • This spot is also called an ovipositor tube,as female bettas lay their eggs inside them.

Body color of bettas

  • Bettas have a natural colouration of green,gray and brown, whereas captive specimens are known for their vivid colors.
  • Male bettas are more colorful than female bettas.Male looks more vibrant than females.They usually display their more vibrant colors to attract female bettas during breeding season.
  • Female bettas are colorful too but they have dull colouration or subdued colouration as compared to male bettas.female bettas tend to choose more colorful males during breeding season.
  • Bettas come in different colors from black, pastel, albino, red, yellow, blue,green,pink,mustard and chocolate colors.

Body stripes in female bettas

  • Body stripes are more common in female bettas.
  • Female bettas are known to display vertical markings on their bodies during mating season.
  • Male bettas don’t show such stripes on their bodies.

Body shape in bettas

  • Male bettas have elongated bodies,which are slightly flatter side to side.
  • Female bettas have a bit shorter and wide bodies.
  • Female bettas have larger bellies than males above their pelvic fins.
  • Male bettas will have less sloped and pointed heads.

Body size in bettas

  • Bettas are generally 2-3 inches in length.
  • Male bettas are bigger in size than female bettas.
  • Mature male bettas are 2.4 to 3.1 inches long.
  • Mature female bettas are 2.25 inches long.
  • Juvenile male and female bettas are of similar sizes. 

Gills size in bettas

  • Male betta fish have larger gills compared to female betta fish.
  • When bettas are aggressive they tend to display their gills. 

Finnage pattern and tails in bettas

  • Bettas are famous for their long attractive finnage patterns.
  • Bettas have short fins naturally whereas captive specimens are known for large and flowing fins.
  • Male bettas have bigger fins than females.
  • Pelvic fins- Male bettas have longer pelvic fins,while female bettas have shorter and skinnier pelvic fins.
  • Anal fins- Male bettas have more boxy and less sloped anal fins than female bettas.Female bettas have more sloped anal fins.
  • Dorsal fins-Male bettas have larger dorsal fins than female bettas.
  • Ventral fins- Males have larger and thicker ventral fins than female bettas.
  • Male bettas have longer tails while female bettas have shorter tails.
  • Male bettas have one disadvantage despite their long flowing fins and beautiful colouration.They get easily attacked by fin-nippers,as it looks very attractive to them and this can cause infection in male bettas.

Beared size and visibility in male bettas

  • Beards are located beneath the gill plate covers called operculum membranes.
  • Beards are present in both male and female bettas.
  • Males have larger beards compared to females.
  • Males beards are visible even if they have not flared their gill plates
  • Female beards are smaller and are not visible.

Flaring pattern in bettas

  • Female bettas show a head down posture during flaring.
  • Male bettas don’t show such head-down postures during flaring.
  • Male bettas display their aggression by flaring their gills.
  • Female bettas flare their gills to show their dominance among females.

Behavior and aggression in bettas

  • Bettas are known as siamese fighting fish for their aggressive behavior.
  • Male bettas are usually more aggressive than female bettas.
  • Female bettas are also aggressive but have lesser aggression than male bettas.
  • More number of male bettas than female bettas in tanks can create fights between in male bettas during breeding.
  • Male bettas fight with each other to death.
  • Male bettas get more aggressive towards species with trailing fins.
  • Female bettas are a little bit social and can coexist with other species in a similar tank.
  • The main reason for their aggression is space,food resources, establishing their territory,mating and bright colors.
  • Bettas are very much particular about their space in aquariums.If their privacy of space is invaded,then they get aggressive.
  • If you are adding a brightly coloured tank mate in their tank,then their aggression gets triggered.
  • Bettas shows their anger and aggression by flaring out their fins.
  • One male betta or one female bettas can be kept together to avoid aggressive behavior.
  • In a community tank, one male betta can be kept with 5 female bettas to avoid aggression.
  • Bettas do get aggressive in overcrowded tanks.This can hamper their lifespans too.

Bubble nest formation in male bettas

  • Male bettas are bubble breeders.
  • Fish that make bubble nests are called aphrophilus.
  • Bubble nests are usually built during breeding time.
  • Only male bettas are supposed to build and blow bubble nests.
  • Bubble nests also known as foam nests are made up of bubble saliva and sometimes with the help of aquatic plants for keeping fish eggs to protect them from enemies.
  • Bubble blowing can be seen occasionally in females too but that would be a rare sight.
  • The male bettas protect the bubble nests and wait for female bettas to spawn on them during breeding time.
  • Male bettas even build bubble nests if there are no females around them.

Parental care in bettas

  • Parental care is a form of altruism,in which parents are involved in caring for their young ones without any selfish motives.
  • It also improve the chance of survival  for their young ones
  • Fish don’t  display a high level of parental care only some fish especially males display parental care.
  • Male bettas display parental care.They take care of eggs and fries.
  • Female bettas don’t display parental care.They are known to eat their own eggs.
  • It is very important to separate female bettas after they hatch.

Why do bettas change their colors?

  • Bettas change their colors in stressful environments or when they are sick.Bettas tend to lose their brightness under extreme stress.
  • Female bettas are known to look more colorful when they are stressed.
  • If you observe such behavior then you make sure to calm them either by removing them to a separate tank or look for what is stressing them out,male bettas or bright lights or other factors.
  • If bettas are fading with age then it’s normal.There is nothing to worry in such cases.Bettas naturally start fading when they are more than 2 years old.
  • Marble bettas are known for changing their colors very often.They have special genes called jumping genes,which is mainly responsible for their color changing behavior.
  • They can change their color pattern multiple times throughout their lifetime.


Gender differentiation is prominent in betta fish and it is only visible when they get matured.

Male bettas are more beautiful,colorful,larger in size,longer flowing fins and are more aggressive.

Female bettas are less colorful,have small fins and show aggression towards other females to look dominant.

Bubble nests are made only by males and parental care is seen only in male bettas.

Female bettas tend to eat their eggs if left with eggs after hatching.

Female bettas are more social and can be kept in community tanks too.

Males tend to kill each other during a fight for females, due to their aggressive behavior.

Avoid keeping mirrors in bettas tanks,as male bettas show aggressive behavior towards mirrors.More aggression is not good for their overall health.Keep them in a stress free environment.

Frequently asked questions

Do male and female bettas have similar eye size?

Eyes of male bettas are larger than females and it is more sticked out from the head.

What is a mirror test in betta fish?

It is a test to know the aggression of bettas towards the mirror.The male bettas tend to be more aggressive when they see mirrors than female bettas.This is also done to differentiate the male and female bettas.

What is the average age of male and female bettas sold in pet shops?

The average of male bettas is 1 year while that of female bettas is 6 months sold in pet shops.Pet shops usually sell more male betta fish because they are more colorful and attractive than female bettas.

What is sorority?

When female bettas live together in groups,especially 6-8 bettas together, then their cohort is called a sorority.