How to Tell If a Swordtail Fish is Male or Female?

How to Tell If a Swordtail Fish is Male or Female?

It’s critical to determine whether a swordtail fish is male or female to maintain the proper balance and look after them as required. So, how can you tell if a swordtail fish is male or female?

There are many physical and behavioral differences between male and female swordtail fish. This can help you identify them.

For example, Male swordtails have long, elongated tails in the shape of a sword. However, female swordtail fish lack this protrusion and have a regular rounded caudal fin.

This article will help you understand how to tell if a swordtail fish is male or female. And tell you every method for sexing swordtail fish.

How to Tell the Difference Between Male and Female Swordtails?

How to Sex Swordtails by Appearance?

Differentiating a male swordtail from a female might be easiest as the signs are visibly seen.

The caudal fins are one of the major differences between male and female swordtail fish. Male swordtails have long, elongated tails in the shape of a sword. However, female swordtail fish lack this protrusion and have a regular rounded caudal fin.

Another way to determine the gender of swordtail fish is by looking at their size, female swordtails are a bit bigger than male swordtails. 

Here are some more physical characteristics to distinguish your fish.

Point of DifferentiationMale Physical CharacteristicsFemale Physical Characteristics
Caudal Fin (The Signature Tail)The signature tail extension, is present only in male swordtail fish.The female swordtail fish lack the tail extension. Instead, they have rounded tail fins.
Anal Fin (Gonopodium)The gonopodium is located on the underside of your swordtail fish’s belly in males. It’s near the end of your swordtail fish’s anus, behind the pelvic fin.The anal fin in females is round and they don’t have a gonopodium.Both pelvic and anal fins in females look alike and are triangular.
Gravid SpotMale swordtails do not have a gravid spot.The gravid area is the womb of a swordtail female during pregnancy, where she carries her young. When a swordtail female is pregnant, the spot grows into a square form and becomes darker in color than the rest of her body.
Body ShapeMale swordtails have a thin, smooth body shape. In addition, they have a and flat stomach area unless they get infected with any disease.
Females are typically larger and bulkier than male swordtails. They have a rounded stomach the section that gives them the appearance of being considerably larger. Their belly becomes rounder during their pregnancy stage than it is normally, as they carry the young ones.
Size5.5 inches in length on average for an adult male.Females grow approximately an inch or two longer than males, reaching 6-7 inches (15-18 cm) long.
ColorMale swordtails are the most attractive and vibrant individuals while looking for males and females from a group.The color of the female swordtail fish is a little drab, and its designs are less defined than those of males.

How to Sex Swordtails by Behavior?

Males are more territorial than females and tend to be more aggressive. If you see a fish chasing other fish around, it is most likely a male.

Female swordtails, on the other hand, are less combative than male swordtails. However, when they’re sick or pregnant, though, they can become quite aggressive.

1. Mating Behaviors

When there are both male and female ones in the tank, the males will swim alongside or chase the females to breed.

On the other side, you will never observe the same conduct from a female during sexual activity.

2. Dominance Behaviors

Male swordtails are known for being aggressive. When they don’t have enough opportunities to breed or are forced to confront other males in the tank, they may become violent.

If you see your swordtails brawling, there’s a good chance the male to female ratio in the tank isn’t properly balanced.

It is recommended to have one male for every two to three females to avoid such behavior.

Why Is Identifying Male and Swordtail Fish Important?

It’s critical to figure out your swordtail fish’s gender. This is due to the following factors:

1. Maintain Safe Male-Female Ratio

The primary goal of identifying male and female swordtail fish is to maintain the appropriate balance in the aquarium.

It would be beneficial if you maintained swordtail fish in a group of four to five individuals, with more females than males. The ratio of male to female swordtail fish should be 1:3.

In the case of having only one female with the male, the male swordtail will pursue and torment her, causing worry.

On the other side, if the two fish are males, they will try to assert dominance and fight with each other.

2. To Pursue Breeding

The swordtail fish is a hardy, adaptable fish. It has the potential to breed quickly and efficiently without requiring any help from you. They can mate and reproduce rapidly in a tank with both male and female specimens.

So if you don’t want your tank to be full of baby swordtails, you should separate the male and female fish. This is why it is important to identify the fish’s gender correctly.

In contrast, if you’re a serious breeder who keeps two male swordtails or two female swordtails in the same tank at once, the breeding will never happen. As a result, it’s critical to distinguish between males and females of this species.

Can Swordtail Fish Change Gender?

Based on this study published in the University of Chicago Press Journals, swordtail can’t change sex. They are born as either male or female and will remain that way throughout their lives. 

However, there are some males who appear like females when they are unmatured, but when they grow old,their colors and other characteristics will show that they are males.

Can I Keep an All-Male Swordtail Tank?

It would be better if you didn’t maintain an all-male swordfish tank.

Male swordtail fish are more vibrant and colorful than female swordtail fish, and they will enhance the appearance of your aquarium.

However, adding numerous male swordtails to your tank has certain disadvantages. Male swordtails are competitive and territorial. Because they exist in a hierarchy, the powerful bully the weak swords.

As a result of this, your swordtail’s health and immune system will be harmed as a consequence of this.

Can I Keep An All-Female Swordtail Tank?

When you maintain an all-female swordtail tank, you’re making a good decision. This is because female swordtails are less aggressive than male swordtails, and they can cohabit peacefully with other community fish.

Female swordtail fish, on the other hand, may store sperm for many inseminations in their bellies. As a result, an all-female swordtail aquarium runs the danger of becoming overpopulated with swordfish fry at some point.

So, the sad reality is even if you have an all-female swordtail tank, you may still end up with baby swordtails.

When is the Best Time to Sex Swordtail Fry?

The ideal time to sex swordtail fry is when they are approximately a month old, at which point the minute distinctions become more obvious, and you can easily determine their gender.

When swordtail fry is born, they all appear to be the same. As a result, it’s difficult to tell males from females.

But, when they get a bit older, distinctions begin to emerge. These variations are minute at first, but as the development continues, they grow more apparent.


What Is the Ideal Number of Swordtails That You Should Keep Together?

The recommended number of swordtails to keep together is five to six. This way, the fish will have enough space to move around and won’t be too crowded.

Can Swordtail Females Have Babies Without Males?

Yes. Females can keep male sperm in their bodies for months after mating. As a result, she will be able to give birth to all of the babies at once in the future, as long as no more male swordtails are introduced into the aquarium.

However, this doesn’t imply that a female swordtail may produce offspring without mating with a male.

Can You Keep 2 Male Swordtails?

It isn’t recommended that you keep two male swordtails together because they are territorial and will fight each other for dominance. This could stress them out and lead to health problems.

If you want to keep two male swordtails, it’s best to have a large tank so that they can each have their own space.

How Do Swordtails Mate?

The males will approach the females from the side, flaunting a sword-like tail fin to capture their attention. They will then touch the underside of the females with their gonopodium, transferring sperm.

Last Words

Swordtails have a number of physical features that can help you determine their gender. However, studying them thoroughly takes time and patience. Please don’t be in a hurry!

We hope you enjoyed this article and that it was helpful. If you have any questions or comments, please feel free to leave them below. Thanks for reading!

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