Fun Swordtail Facts For Kids | Kidadl


Fun Swordtail Facts For Kids

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The swordtail (Xiphophorus hellerii) is a freshwater fish popular among tropical fish. Swordtail fish are elongated fish, which can grow up to 5 in (13 cm) in length with males having a long sword-like lower tail fin lobe. These species are related to the platy and are used in many medical and genetic research. Naturally, these species in the wild are olive green in color, but they are also found in many color varieties such as red, black, and orange because of the large-scale captive breeding.

Swordtails are extremely famous as pets in a large tank as they are low maintenance. They are great as livebearers for breeders who want to breed more of these fish to sell. Swordtails live peacefully with other swordtails but try to fight and kill other species.

Many different types of swordtails are available all over the world as they have been cross-bred with other species, and because of this, their color spectrum keeps rising, making them one of the most renowned pet fish!

If you liked these facts about swordtail, then you'll surely like these facts about firefish and angelfish too!

Fun Swordtail Facts For Kids

What do they prey on?


What do they eat?


Average litter size?


How much do they weigh?

0.2 lb (100 g)

How long are they?

6.3 in (16 cm)

How tall are they?


What do they look like?

Olive Green

Skin Type

Wet, Slimy Scales

What were their main threats?


What is their conservation status?

Least Concern

Where you'll find them?

Streams And Rivers


Mexico, Honduras, Veracruz









Swordtail Interesting Facts

What type of animal is a swordtail?

A swordtail is a type of freshwater fish that is common as a community aquarium fish. They have unique fins that come in various colors, due to which they are also known as yellow swordtail, blue swordtail, red swordtail fish, or red velvet swordtail. Mollies are another group of livebearer fish like the swordtail.

What class of animal does a swordtail belong to?

Swordtail belongs to the class of Actinopterygii, as they are ray-finned fish. Actinopterygii is divided into two different classes of Cladistia and Actinopteri. Actinopterygians comprise almost 30,000 species of fish, including piranhas and other species.

How many swordtails are there in the world?

Unfortunately, there is no accurate count on the population of swordtail fish. As these species are easily available and are bred in private aquariums, it is impossible to know the exact population.

Where does a swordtail live?

Swordtails are freshwater fish and live in favorable breeding grounds in brackish habitats with lots of vegetation and plants around them to hide from predators, sunlight, and flowing water. They are mostly found in fish tanks and aquariums now since they are popular aquarium fish.

What is a swordtail's habitat?

The natural habitat of these fish is in Central America and North America, where they were discovered in 1848. In the wild, they have olive green bodies that have red stripes. Swordtails quickly became an invasive species worldwide due to their wide range of color patterns, making them great for fish lovers.

Who do swordtails live with?

Swordtail fish live in a group but do not school in one. They are robust in nature and can handle a wide range of temperatures.

Swordtails are territorial in nature, and males can get aggressive when another swordtail gets inside their territory and shows aggression. So, if you happen to buy swordtails for your aquarium, make sure you keep a single male or have enough hiding spots or toys in the tank to divert their minds.

How long does a swordtail live?

Swordtails are used as livebearers and used for breeding, so the strain on the female to give birth to babies affects swordtail lifespan. Their color becomes dull, and they lose energy when they grow old. These livebearers keep declining in health and eventually die after three or four years. Some, however, die earlier from the strain they get from too much breeding.

How do they reproduce?

Swordtails are livebearers, meaning that the female, during breeding, will carry her eggs inside her body and will give birth to live young.

Males use their anal fin to impregnated the female during breeding, and the female will birth 50-100 fry. After this, she might birth another batch of fry after four to six weeks.

In swordtail fish, the presence of a robust male will increase the maturity of the females causing more babies to be born if a male mates with multiple females. Signs of pregnancy in the female are visible as there will be a dark gravid spot near her anal fin.

What is their conservation status?

Swordtail fish are listed as a species of Least Concern by the IUCN Red List. These fish are abundant in nature in the range of South and Central America and are one of the most common fish species that are used in breeding as livebearers in a fish tank or an aquarium. Since this breed of fish is often cross-bred with other fish, due to which their population is nowhere near extinction.

Swordtail Fun Facts

What do swordtails look like?

Swordtail fish care tips are educational!

Swordtail fish have various colors, the most common being olive green and yellow. They have red streaks running down their sides and are called red swordtails or green swordtails.

Their name swordtail comes from the Greek word 'Xiphophorus', which translates to sword-bearer and is a reference to the extended part that is found at the lower part of their caudal fin which resembles a sword. Males can be distinguished from the female by the presence of a gonopodium (the reproductive organ used for copulation).

Due to cross-breeding with different fish, there are several colors that this fish comes in. The koi swordtail, Kohaku swordtail, pineapple swordtail, calico swordtail, pointed swordtail, neon swordtail, and the lyretail swordtail are some swordtails that can be produced by cross-breeding swordtail fish with other fish.

How cute are they?

Swordtails are extremely cute! Their color shades and the way they swim around minding their own business add to their cuteness factor!

How do they communicate?

All fish have otoliths consisting of a sensory epithelium made up of calcareous otoliths and their hair cells that they used to communicate with each other.

How big is a swordtail?

Since these fish show sexual dimorphism, swordtail fish size can differ from male to female. Females are larger than males and grow up to 6.3 in (16 cm), compared to the males who grow 5.5 in (13.9 cm)! They are twice the size of a Siamese fighting fish.

How fast can a swordtail swim?

No apt data can be found to state how fast these fish can swim. The fastest ocean fish is the sailfish that travels at up to 70 mph (112 kph)!

How much does a swordtail weigh?

Swordtails weigh around 0.2 lb (100 g). However, this weight can vary from freshwater swordtail to swordtail guppies.

What are the male and female names of the species?

No particular name has been assigned to either sex of this fish.

What would you call a baby swordtail?

Newborn swordtail babies are called fry. They look like newly hatched brine shrimp. When they are born, proper feeding habits should be uses and they should be fed live meat and protein, which can include mosquito larvae and bloodworms.

Right after birth, these fries start searching for food to eat!

What do they eat?

Swordtails are omnivorous in nature and will eat foods that consist of insects and plant particles. In an aquarium, they should be provided with live food that has a small enough body for the fish and the babies to eat.

Commerical foods like flakes are great for feeding them as they have meat and live foods in them that are necessary for the growth of babies and adults.

Are they aggressive?

Swordtails like to live a peaceful life and are social and enjoy good company, especially when they are housed with other swordtails or similar species like angelfish, platies, and mollies.

The male red wag swordtail can show aggression towards other swordtails as they are territorial, due to which not more than one male should be kept in the same aquarium. They are also known to be great jumpers, so make sure to cover your aquarium or tank to prevent them from escaping and dying in the process.

Would they make a good pet?

Yes, they are good pets. So much so that they are one of the most found fish in an aquarium ecosystem. The minimum requirement for these fish is a 20 gal (75 l) tank! A single swordtail would need a 15 gal (57 l) tank, and you can keep a pair in a 20 gal (75 l) tank. If the tank is too cramped, males can get aggressive. Some tank mates for them are platy, lemon tetras, danio, and dwarf gouramis.

Swordtail fish care is easy as you need to keep a big aquarium because of its small size. A large aquarium is more than enough for them to swim freely and not harass other fish, making them great pets in a community tank. Males and females should be kept at a ratio of 4:1 among swordtails and tank mates if any. Please make sure you have good water as they require alkaline and medium-hard water as long as it is neither too soft, nor too acidic. Temperatures should be around 71.5-82 ° F (22-28 °C).

Did you know...

Green swordtail (X. hellerii) has slowly turned out to be a pest as an introduced species in several countries. This is because they reproduce in high numbers, and they and the swordtail fry eat up a large number of foods and create scarcity.

Swordtails like to live in water sources that have a high mineral count!

Some of the known swordtail types are the painted swordtail, hi fin swordtail, lemon swordtail, sailfin swordtail, velvet wag swordtail, vampire swordtail and the black swordtail fish.

Like most of the livebearers, a female swordtail lacks maternal instincts and thus, will consume her fry after birth. This is mainly due to a lack of food sources. Even with abundant food sources, it cannot be said if the female will eat her fry or not.

In order to breed a swordtail-platy hybrid, there is no set specific condition and just putting them together in a tank with male platy and a female swordtail or female platy and a male swordtail is enough as these fish belong to the same genus. No extra effort or paternal care is required to make them breed.

Females do not have the 'sword' at the end of their bodies. This can be a great way to differentiate between male swordtails and females.

Platy-swordtail hybrid is one of the most common cross-breeds that can be found in pet stores!

What fish are swordtails often found with in nature?

Wild swordtails often share feeding and breeding grounds with their cousins, like the mollies, platies, and angelfish. They co-exist peacefully with them in the wild and can be tank mates with them too in an aquarium or fish tank.

How have swordtails helped scientific research?

For nearly 100 years, swordtails have been used as research subjects thanks to their unique features. The Montezuma swordtail, one of the swordtail species, has been studied by scientists and researchers in an effort to curb cancer signs in humans. This is because they are often plagued by skin cancer which is the result of intermixing within species and the females give birth to mixed fry that is not likely to survive due to this intermixing. Hence, swordtail genomes have been used to study skin cancer and ways to prevent it, trying to get a lead on new therapies for treating cancer in humans.

Swordtails are also used as a model organism in studies leading to the reasons behind mate preference and conflict in these fish.

Here at Kidadl, we have carefully created lots of interesting family-friendly animal facts for everyone to discover! Learn more about some other fish from our diamond tetra facts and cherry barb facts pages.

You can even occupy yourself at home by coloring in one of our free printable Swordtail coloring pages.

Written By
Moumita Dutta

Moumita is a multilingual content writer and editor. She has a PostGraduate Diploma in sports management, which enhanced her sports journalism skills, as well as a degree in journalism and mass communication. She's good at writing about sports and sporting heroes. Moumita has worked with many soccer teams and produced match reports, and sports is her primary passion.

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