Swordtail Fish – scientifically known as the Xiphophorus hellerii – is one of the most beautiful aquarium fish species, known for their beautiful tails that are shaped like swords, hence the name Swordtail Fish. It is a popular aquarium fish that is loved by the fish keepers in the United States and other parts of the world. It has multiple trade names including Green Swordtail Fish, and Red Swordtail Fish, these names are based on their colorful appearance. This fish species has an extra-large tail fin that becomes thin and long with a pointy end similar to a sword.

Pharaoh Hound at the English-language Wikipedia, CC BY-SA 3.0, via Wikimedia Commons

This gives the fish a unique appearance, apart from the tail, other parts of their body are similar to most other normal fish species from their family. Colorful variants of the Swordtail Fish occur naturally, but some varieties have been selectively bred to produce specific colors and other appearance features. This fish also has a unique breeding pattern, which makes it easy to breed in captivity. That is why it is known as a good species of fish for those who want to observe and learn about fish breeding. Fish from this species is known as the livebearers. As it is a popular fish species, you can find them in almost all online and offline fish stores. Here is a complete guide about taking care of the Swordtail Fish.

Basic Facts Table

LifespanUp to five years.
SizeUp to 7 inches.
ColorsRed, Olive Green, Brown.
Freshwater or SaltwaterFreshwater
Care LevelMinimum.
CompatibilityPeaceful fish communities.

Tank Companions

Here is a list of the possible tank mates or tank companions of the Swordtail Fish.

  • Angelfish
  • Cory Catfish
  • Rosy Barbs
  • Neon Tetra
  • Kuhli Loach
  • Pearl Danio
  • Dwarf Gouramis
  • Platy Fish
  • Molly Fish
  • Otocinclus

How To Select Tank Companions?

There are a lot of potential tank mates and companions for the Swordtail Fish. This is because it is a medium-sized peaceful fish species. It does not attack or bother the members of its tank and lives peacefully in the middle and near the bottom of the tank. Also, they cannot defend themselves from the attacks of the predators, so, you should not put them with any of the aggressive fish species. When it comes to selecting a potential tank companion or tank mate, there are three important factors that you need to consider. These include the size, living conditions, and temperament or behavior of the fish. Here is why you need to consider these three factors.

If you paired the Swordtail Fish with a wrong-sized fish, for example, a very large fish species. Larger species of fish tend to be aggressive, and they attack the smaller fish species in the tank. For that reason, if you paired them with the Swordtail Fish, the peaceful environment of your tank would be destroyed. Also, it would give rise to tension, and stress in your Swordtail Fish and that can lead to health issues and the death of your fish. Apart from this, you cannot put a very small fish species in the tank of a Swordtail Fish. Although they are a peaceful species of fish that does not attack the smaller fish species, they are also omnivore species of fish that eat everything.

So, if there is a food shortage in your tank, there is a chance that your Swordtail Fish would eat the smaller companions. Apart from size, you also need to consider the living conditions. This is important because you cannot pair the two species of fish that live in different conditions. For example, you cannot pair a marine fish with freshwater fish. Also, you cannot pair a fish that lives in a cold area with a fish from a tropical region. The difference in living conditions would kill one or the other fish. So, it is important to consider the living conditions of fish species and select the one that can live in similar conditions.

The third most important factor to consider for the tank companion of Swordtail Fish is the temperament of the tank companion. As you know that the Swordtail Fish is one of the most peaceful fish species, it cannot defend itself if it is attacked. Mostly, they try to evade the situation and hide. So, if you introduced an aggressive fish species in their tank, you will be putting them at risk. Constant attacks from their tank mates can lead to severe stress and health issues. It can even lead to the death of Swordtail Fish. For that reason, it is important to select a peaceful fish species and avoid an aggressive tank companion. If you follow these guidelines, you can select a variety of tank mates for the Swordtail Fish.

Species Overview

The Swordtail Fish is one of the most beautiful fish species that has multiple color variants, and each color variant is known for a specific color. For example, the red Swordtail Fish is known for its reddish outlook, meanwhile, the green Swordtail Fish is known for its olive-green color. You can find the Swordtail Fish of the color of your choice. It is one of the most common fish species that is used in aquariums worldwide. It is popular because it has a beautiful appearance, peaceful nature, and also it is easy to care for.

According to fish keepers, it is also a favorite choice for the new fish keepers who want to observe or want to learn about fish breeding. Because this is a fish species that can breed easily without outside intervention. It allows the new fish keepers to observe their breeding pattern and use it for the breeding of other fish species. It is a fish species that is also known as a model organism because it has been a subject of scientific research. This fish species has also been subject to multiple breeding programs where specific traits of the Swordtail Fish were perfected.

Below are further details about the fish’s appearance, nativity, lifespan, and natural habitat. You need to know these details to create a perfect habitat for your fish.


The Swordtail Fish has a beautiful elongated appearance. In this species, the long sword-like fin is only seen in the male. Females from this species lack this long sword-like tail and that is what helps you identify the males and females separately. It is a very important detail to know if you are planning on breeding the Swordtail Fish in your tank. Apart from this, the male and female bodies are similar as they have similar shapes, sizes, and colors. Swordtail Fish have a streamlined body shape, with a long caudal fin, and an upward mouth.

As mentioned in the paragraphs above, the Swordtail Fish comes in multiple colors as there are a lot of varieties. Two main variants of the Swordtail Fish are red Swordtail Fish and green Swordtail Fish. Wild Swordtail Fish is known for its olive-green to brown appearance. Meanwhile, the most common aquarium variants are brighter as compared to the wild specimens. This is because these aquarium specimens have been through a lot of in-breeding, and selective breeding to perfect their colors.

A lot of other varieties with multiple colors and patterns are also available because this fish has been cross-bred with many other fish species. Black and orange-colored Swordtail Fish are known as some of the exotic choices. These are available but only in a few places. The shape, and size of these variants also remain the same, meanwhile, the major change is in the color of the fish.

The size of Swordtail Fish depends on the type of care that you can provide them. The average size of this species is about 5.5 inches in length and two inches in height. But most of them only reach about 5 to 6 inches. The maximum size limit for a healthy-grown Swordtail Fish is about 7 inches. But they only reach that size limit if they are provided a perfect habitat and a very large tank. According to most fish keepers, their size depends on the care, and the size of the tank. For example, if you keep them in a small tank, they would not grow longer than 3 to 5 inches. But if you keep them in a spacious tank where they can swim freely, you would notice that more Swordtail Fish will reach a 5 to 6 inches limit.


The Swordtail Fish originates from South and Central America, in Hundorous, Veracruz, and Mexico. It lives in the rivers and freshwater streams in these regions. Most of the time these fish are known for swimming near the bottom of these fast-flowing rivers, and streams. The Swordtail Fish is also found in canals and hot springs in these regions. It prefers living in those places where it can easily find food, and where there is space for it to hide from predators.

Natural Habitat

The Swordtail Fish likes to live in warm climates, where it has access to vegetative shelter in the bottom of the rivers, streams, and hot springs. Unlike most small fish species, this fish likes to live in those places where the flow of water is fast. Their streamlined bodies allow them to swim both ways, in the direction of the stream, and against the stream. In the wild habitats, this fish eats everything that it can find including the vegetation, algae, and small crustaceans and worms.

This fish can adapt to the changing conditions in its habitat. This makes it a fish species that is easy to care for because you will not have to worry about the changing conditions inside your tank. Also, this fish breeds a lot in its native habitat. This helps them replenish the overall number of their population. In their natural habitats, these fish can live for more than 4-5 years. So, if you provide them with good living conditions, you can extend their lifespan from three to five years.

Swordtail Fish Lifespan

As mentioned in the paragraph earlier, this fish can live for more than 5 years in its natural habitat. But inside the tank, its lifespan depends on the care that you will provide them. So, if you are providing them minimal care, your fish can live for more than two years. With good care, you can extend this lifespan by one year and your fish would be able to stay alive for three years or more. But if you provide them excellent living conditions, and care, your fish would live for more than years. Meanwhile, the average lifespan of the Swordtail Fish is about 4 years. You may notice that your colored variants of the Swordtail Fish may not for four years.

This is because of genetic mutations. These genetic mutations make them more prone to parasites, and infectious diseases and that is why they may die quickly. If you have a colored variant or a selectively bred variant of the Swordtail Fish, make sure that you do not put anything in your tank that has not been cleaned and disinfected properly. For example, a lot of aquarists use the same decorations for multiple tanks. This can cause parasites and bacterial infections to move from one tank to another. You should avoid doing that to make sure that your fish remains healthy.

Habitat and Tank Conditions

The Swordtail Fish needs a specific type of habitat and living conditions inside the tank. You need to create this habitat and tank condition for them before putting them inside your aquarium. The main four things to consider for this include the tank size, tank setup, water parameters, water conditions, and the water source. Here are further details about these.

Tank Size

You need to start with the tank size. As mentioned above, the tank size of your aquarium has a lot of importance for the fish. For example, it controls the health, and size of the fish inside the tank and can determine the lifespan of your fish as well. You need a spacious tank to keep these large fish. According to some expert fish keepers, if you keep the Swordtail Fish in a small tank, they would not be able to grow in size and reach their potential size. But if you provide them with a large tank where they can swim and explore a large area, they will grow faster and reach more than 6 inches in size.

There are a few recommended sizes for the tank of Swordtail Fish. For example, most aquarists recommend a tank of 50 gallons or more for a healthy population of Swordtail Fish. You should make sure that your tank is not high, instead, it is long and wide. This would create more space in the bottom layer of the Swordtail Fish to explore. But, this is not the only size of the tank that you can use. Some people have had success at keeping the Swordtail Fish in smaller tanks of 10 to 20 gallons size. But this is not a recommended size for a group of Swordtail Fish. In these smaller tanks, you can only keep two to three individuals. If you want to keep more than this, you will have to select a larger tank for your Swordtail Fish community.

Here are a few things that can help you calculate the perfect size for the tank of Swordtail Fish. First, you need to know the number of fish that you want to keep inside your tank. If you want to keep more than one species, know their fish per gallons ratio. Get an average fish per gallons ratio for your species, and then multiply it with the number of total fish that you want to keep in your tank.

Tank Setup

When you start creating the tank setup for the Swordtail Fish, you need to start from the bottom layer. First, you should scatter stones, pebbles, and a small amount of sand in the bottom layer. Make sure that you do not put anything sharp in this layer because it can hurt the fish. A bottom layer is a place where this fish spends most of its time. So, it needs to be better and more comfortable. Also, you need to plant some aquarium plants at the bottom of the tank.

You can select from a wide variety of aquatic plants. It is better to use real plants instead of silk plants because silk plants would not be producing oxygen. Also, they would need cleaning while the real plants would be acting as cleaners of the tank. Also, they would provide hiding spots for the fish to explore and use as a shelter. Apart from putting plants, and decorations in the tank, you also need to put a filtration system inside the tank.

The filtration system has many benefits, from cleaning water to creating flow inside the tank. You should use a strong water filter to maintain a higher flow rate, and provide more oxygen to your Swordtail Fish inside the aquarium. Apart from this, you also need to put a temperature monitoring and controlling device. These will allow you to maintain the temperature of your aquarium. You can also use a lid to cover the top of the aquarium, and also use standard aquarium lighting to keep the tank lit during the day.

Water Conditions/Parameters

There are a few water parameters that you need to maintain inside your tank.  These parameters include the temperature of the water, pH level of the water, and hardness of water inside your aquariums. These parameters are important to maintaining because they directly impact the health and lifespan of your fish. Here are the optimal ranges of these parameters that you need to maintain.

  • The temperature of the water should be maintained between 75 to 79 degrees Fahrenheit.
  • The hardness of the water inside the aquarium should be maintained between 12 to 35 dGH.
  • The pH of the water should be kept neutral or close to neutral. This is a slightly alkaline and not an acidic environment.

If you don’t maintain these parameters, your fish will likely die prematurely. This is because of all of these parameters of quality of water, which causes health issues in the fish. Changes in these parameters can kill your fish because these changes will change the chemistry of water, thus changing the internal chemistry of the fish. This is why you need to make sure that these parameters remain within the given ranges all the time.

Water Source

You can use water from any source including your tap, local rivers, ponds, lakes, freshwater streams, and any other freshwater source. The only thing you need to do is to make sure that the water you are adding inside the tank has been tested. If you do not test the water, there is a chance that you might end up using contaminated water. For example, water from your tap and local reservoirs may contain chemicals such as chlorine, and other harmful chemicals that are added to kill bacteria in the water. But these chemicals are also harmful to the fish. So, you need to clean your water before adding it to the tank. You can do this by using the RO or reverse osmosis method of water filtration.

Behavior and Temperament

It is one of the most beautiful fish species of large size that is also peaceful. The Swordtail Fish is known for being joyous and social. It likes the presence of other fish inside the tank. Hence, you should always keep it with other fish species. You should never leave them alone in a tank, as it can cause several issues such as stress, tension, and depression.

When kept inside a tank, this fish species gets along very well with the members of its fish species and the members of other fish species as well. It shows the social behavior of schooling and shoaling if the tank is large enough. Otherwise, you will see them foraging in the bottom layer of the tank.

Breeding Swordtail Fish

As mentioned above, the Swordtail Fish is one of the easy-to-breed fish species. It does not require special conditions to breed. You just need to make sure that your tank is clean, and conditions are within the optimal range during their breeding season. Here are a few tips that will help you increase your success rate for breeding Swordtail Fish.

  • It is recommended that you create a separate breeding tank where you can control the whole breeding process. You can breed them without a special breeding tank but it is better to have one.
  • This fish is a livebearer, meaning that they carry their eggs and babies inside. The male and female spawn and the female take care of the fertilized egg within its body.
  • It breeds multiple times, it produces multiple Fry during each time. Female Swordtail Fish would carry the babies inside for 28 days, and after that, they will give birth.

Eggs and Fry Care

Once the Fry comes out of the female Swordtail Fish, it needs protection from the aggressive members of the tank, and large members of the tank that might attack them. The female Swordtail Fish would try to protect the babies and would provide them the food. But you can also feed them a specialized Fry diet. It would keep them healthy and would allow them to grow in size quickly.

Diet of Swordtail Fish

The Swordtail Fish is an omnivorous fish species, omnivore species eat everything, including vegetation, and meat-based foods. So, you can feed your Swordtail Fish anything, including vegetables, algae flakes, meat pellets, frozen meat, worms, and live crustaceans. These are medium-sized fish species and they need more food. So, you should feed them twice a day.

Diseases of Swordtail Fish

Although it is immune to many infectious problems and diseases, some diseases can attack the population of Swordtail Fish in your tank. Here is a list of them and how you can treat them.

  • Skinny Disease: This is a deadly disease that causes your fish to lose weight. You will notice some of your fish are thin as compared to the other members. It is caused by several bacterial, and fungal infections that impact the digestive tract of the fish. It is treatable, but you will have to improve the conditions of your tank.
  • Shimmies Disease: It is also a deadly disease that has no solution, apart from the cleaning of the environment to protect the other members from the spread of this disease.
  • Fin and Tail Rot: As the name suggests, this is a disease in which the fin and tail of your fish would start to rot. This happens because of the unhygienic conditions, and fish biting the tail and fin of the Swordtail Fish.

What is the Ideal Size For The Tank?

There is no single ideal size for the tank of Swordtail Fish. This is because the size depends on the number of fish that you are keeping in that tank. You need to know the number of fish that you want to keep in that tank to calculate the ideal size of the tank. The smallest tank that you can use for keeping the Swordtail Fish is 20 gallons, but it is not a recommended size. Recommended sizes for the Swordtail Fish tank start from 30 gallons.

Is Swordtail Fish Saltwater or Freshwater Species?

The Swordtail Fish is a freshwater fish species.

Is Swordtail Fish a schooling species or not?

This fish species has social interactions with the members of its species, but it is not a schooling or shoaling type of behavior. They swim, feed, and reproduce in groups, but they do not display any signs of schooling or schooling.

Conclusion – Is Swordtail Fish Suitable For Your Aquarium?

If you love the beautiful fish species, with unique features, characteristics, and peaceful behavior, then it is the right choice for your aquarium. This is because this is a fish species that is easy to care for, so even if you are a new or experienced fish keeper, you can keep it. Also, you can enjoy its presence if you like watching fish species swim. It has a streamlined body that allows this fish to swim at a faster speed as compared to other large fish species of similar size. It will keep you entertained for hours.


Question: How are female and male Swordtail Fish different?

Answer: Female Swordtail Fish and Male Swordtail Fish are different from one another. This difference can be seen in the size of their caudal fin. In Male Swordtail Fish it is longer, meanwhile, in females it is short. But the overall size of the female is larger than the male. These characteristics help identify the male and female for breeding.

Question: Which is the most common color in Swordtail Fish?

Answer: Green Swordtail Fish is the most common variety of aquarium fish. Other popular variants include red, orange, and black. There are also some exotic variants that you can buy from special sources.

Question: What is the average size of Swordtail Fish?

Answer: The Average size of the Male Swordtail Fish is about 14 cm or 5.5 inches, meanwhile the females are longer and can be 16 cm or 6 inches.

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