Swordtail Fish Species Overview, Care & Breeding Guide

If you are looking for an active, harmonious fish for your freshwater tank, you must know about the swordtail fish.

The fish is extremely hardy and disease-resistant, thus best suited for beginners. It’s also a delightful experience to watch this super playful fish darting around the aquarium.

So, if you’re ready to have a few of them, then keep reading!

What is a Swordtail Fish?

A sword tail fish, as the name suggests, is a fish that is popular for its tail which looks like a sword. Apart from this, the fish does not catch any diseases easily.

OriginNorth and Central America: River Nantla, Veracruz, Mexico to northwestern Honduras, Belize, and Guatemala; Nautla and Sarstún Rivers; Lake Catemaco
Scientific NameXiphophorus hellerii
Common NamesSwordtails, red swordtail, green swordtail
IUCN Red List StatusLeast Concern
AppearanceOlive green color, streamlined torpedo-shaped body and upturned mouth.
SizeAn average 10 cm (4 inches)
LifespanUsually 3 years in captivity, 5 years with the best care
TemperamentPeaceful, males can be territorial and aggressive toward other males
Tank LevelMid and upper-level dwellers
Water Temperature21-26 °C (70-79 °F)
pH Level7-8
Water Hardness10-15 dGH
Care LevelVery easy
Minimum Tank Size20-gallon tank for one fish. Extra 6 gallons per additional fish
Tank EnvironmentHeavily planted tank with caves, smooth rocks, driftwood, or non-toxic ceramic decorative pieces
Tank MatesPeaceful fish of similar size

What is the natural habitat of Swordtail Fish?

Swordtail fish is native to North and Central America, stretching from River Nantla in Veracruz, Mexico, to northwestern Honduras.

It’s also found in Belize and Guatemala, including rivers like Balsas, Nautla, Sarstún, and Catemaco Lakes.

The fish inhabit freshwater and brackish environments, favoring rapidly flowing streams and rivers with dense vegetation.

It has become invasive in several countries worldwide, including South Africa, Argentina, and Australia, posing a threat to native species.

As per the 2018 assessment of IUCN Red List Status of Threatened Species, the species is labeled Least Concern.

Which family does Swordtail Fish belong?

The species belongs to the Cyprinodontiformes order and Poeciliidae family. Its binomial name is Xiphophorus hellerii, whereas it’s popular worldwide as swordtail, red swordtail, and green swordtail.

In the Xiphophorus genus, there are only two types of species – platy fish and swordtail fish. The green swordtail is a type species of this genus.

Swordtails are often confused with platy fish as they look quite similar. So, a few ways to differentiate between the two species is that platies are much more compact in size. But swordtails have an elongated and slender body.

Further, male swordtails have a sword-like extension, which the male platies don’t have. And the female swordtails have a slightly longer dorsal than female platies.

However, if a pet store houses swordtails and platies together, they may hybridize, making differentiation impossible.

Fun Fact: The scientific name of the green swordtail, “Xiphophorus,” originates from Greek and translates to “sword-bearer,” referring to its tail fin’s extension.

How does Swordtail Fish Look?

Swordtail fish in aquarium

Now, if you want to learn more about their looks and behaviors, let’s dive right in!

What is the size of a Swordtail Fish?

The male swordtail grows up to 14 cm (5.5 in), while the female can reach 16 cm (6.3 in). On average, this fish is around 10 cm (4 in) long.

What is the color of a Swordtail Fish?

The naturally found swordtail fish is olive green. It also sports dark-red or brown lateral stripes and speckles on the dorsal and, sometimes, caudal fins.

Due to cross-breeding, there are many variants of captivity-bred swordtails available. These variants differ in color, patterns, and fin structures.

The only common trait among all variants is their dark-red or brown lateral stripe.

What are the features of a Swordtail Fish?

The swordtail fish has a streamlined torpedo-shaped body, wide tailfin, pointy snout, and upturned mouth. There are slight variations in fin shapes due to selective breeding.

It has a small hump where the dorsal fin attaches to the head. There are seven fins in total, including dorsal, caudal, paired pectoral, pelvic, and a single anal fin.

The typical fish has a short triangular dorsal fin and a pointed caudal fin with an extended lower half.

On hi-fin swordtails, the dorsal fin is tall and wide, resembling a sail. Longfin swordtails have all seven fins elongated and trailing behind their bodies, whereas lyretail swordtails feature a split caudal fin with extensions at both ends.

How is a Swordtail Fish male different from the female?

The tail of a male is long and extended, like a sword, which is generally yellow with black edges.

Females are larger with shorter, rounded tails and devoid of this tail extension.

What is the behavior of Swordtail Fish?

Green swordtail is social and peaceful, typically found in small groups. It’s an active swimmer and explores the middle and upper parts of the tank, occasionally venturing to the bottom for food. It enjoys the company of the same or similar species.

The male fish can be slightly territorial and aggressive towards each other, showing chasing and nipping, mainly due to competition for mates.

It’s recommended to maintain a ratio of one male to several females to prevent male aggression.

The fish is not particularly timid or shy, except in the presence of large or hyperactive fish species.

What is the Lifespan of Swordtail Fish?

Many fish keepers can sustain the fish for a maximum of 3 years. However, as per my experience, with extremely careful maintenance, it can survive for up to 5 years.

Author’s Note: Coming from tropical waters, these fish need warm water to thrive. If the temperature drops below 69 °F, an adjustable heater suitable for your tank size is necessary for their survival.

How to take care of Swordtail Fish?

Baby swordtail fish with adult

Now, If you’re ready to bring this fish home, let’s start creating its new habitat!

What is the Tank Size for Swordtail Fish?

To ensure a healthy and stress-free environment, invest in a 20-gallon tank for a single green swordtail fish.

The species should be kept in a group of 4-6 fish, but make sure to add at least 6 gallons for each additional fish.

An elongated tank shape is preferable, as it gives the active fish more room to swim and explore.

What is the Water Chemistry for Swordtail Fish tank?

This fish is hardy, but sudden water parameter changes can harm it. So, for your fin buddy’s healthy life, here’s what you must maintain instead:

  • pH Levels: 7-8
  • Water Temperature: 21-26 °C (70-79 °F)
  • Water Hardness: 10-15 dGH
  • Ammonia: 0 ppm
  • Nitrite: 0 ppm
  • Nitrate: Below 20 ppm

What is the Tank Environment for Swordtail Fish?

Aquarium landscaping impacts your fish’s well-being and mood. Let’s create the best environment for them!

What are the Substrate required for Swordtail Fish?

There’s no strong substrate preferences for this species. But smooth, dark sand or fine gravel can enhance their appearance. It’s also essential to keep the substrate clean for their health.

Which Plants should be kept in Swordtail Fish Tank?

The fish appreciates a densely vegetated tank with open space for swimming. You can keep live or artificial silk plants.

Live plants especially enhance the beauty of the fish tank and provide practical advantages such as cover for the fish, improved oxygenation, and absorption of nitrates.

Some compatible plants for green swordtails include:

  • Java fern
  • Anubias nana
  • Dwarf hairgrass
  • Guppy grass
  • Java moss
  • Hornwort
  • Water sprite
  • Amazon frogbit
  • Scarlet temples

Which type of Lighting is needed for Swordtail Fish?

Use fluorescent lighting for your tank, providing 8-10 hours of moderate lighting during the day. Avoid extended bright lighting periods to prevent algae overgrowth and stress for the fish.

What Décor is required for Swordtail Fish tank?

Create hiding spots for your green swordtail fish using caves, smooth rocks, driftwood, or non-toxic ceramic pieces.

These hiding spots provide safety and enhance your tank’s appearance. Further, avoid sharp objects that can damage its delicate fins.

What type of filter is required for Swordtail Fish?

Find a good hang-on-back or canister filter that can handle at least double the tank’s size. This keeps the water clean by removing waste and toxins.

You can use air stones or place the filter output near the water’s surface for more aeration. Perform biweekly (25%) water changes and consider weekly changes if your tank has many plants or fish.

What is the Water Flow Rate for Swordtail Fish?

The fish can thrive in aquariums with high to moderate flow, similar to their natural habitat. You can achieve this with filters, powerheads, and wavemakers. But consider the needs of other community fish in the tank.

Fish Care Tip: Before adding fish, cycle your green swordtail aquarium by adding a small amount of fish food daily for a week. This will create ammonia, which is essential for nitrifying bacteria. Introduce your pet fish once ammonia levels stabilize.

What does Swordtail Fish eat?

Swordtail fish is omnivorous in its natural habitat, and its diet typically consists of a wide range of foods. It feeds on worms, crustaceans, insects, bug larvae, tiny microorganisms, shrimps, snails, and plant matter. It also grazes on algae and nips the plants.

Its diet varies seasonally, with a preference for live prey in the spring and summer and more plant-based food in the fall and winter.

In captivity, this fish should be provided with a diverse diet consisting of approximately 50% protein, followed by healthy fats, fiber, and vitamins.

Here is a list of foods suitable for these fish:

  • Brine shrimp
  • Daphnia
  • Bloodworms
  • Water fleas
  • Tubifex
  • Live worms
  • Zooplankton
  • Crickets
  • Live plankton
  • Earthworms
  • Frozen mosquito larvae
  • Frozen krill
  • Frozen worms
  • Frozen shrimp
  • Flake foods
  • Pellets
  • Seaweed
  • White worm
  • Mysis shrimp – live and frozen
  • Spirulina
  • Kelp meal
  • Peas
  • Spinach leaves
  • Zucchini
  • Cucumber
  • Broccoli
  • Algae wafers
  • Tomato
  • Vitamins or food containing vitamin B12

Feed the fish three times a day with the quantity that they can consume in under 3 minutes. Promptly remove any uneaten food to maintain water quality.

What are the Tank Mates for Swordtail Fish?

Stick to similarly sized fish with the same easy-going temperament for a tank with swordtail fish like the following:

Though it does well with other livebearers like platy, it may hybridize with them, causing the tank to overpopulate quickly.

The fish tends to eat smaller invertebrates, but they can coexist with assassin snails and amano shrimps.

Which Tank Mates to Avoid for Swordtail Fish?

However, you must avoid housing the following together:

  • Predatory fish (eg: Oscars, arowanas, or piranhas): They might prey on your pet fish.
  • Aggressive or territorial fish (eg: Jack Dempsey, African cichlids, or Siamese fighting fish): They may harm the timid pet that can’t defend themselves
  • Nipping fish (eg: tiger barbs and serpae tetras): They might injure your pet fish.
  • Large slow-moving fish (eg: Goldfish): They can be nipped by your pet fish and get stressed and sick.

What are Common Diseases in Swordtail Fish?

Swordtails are quite hardy and resistant to diseases, but they are not immune, so it’s important to be ready to treat the following issues:

Disease NameCausesSymptomsTreatment
Ich (White Spots)Protozoan parasiteWhite spots on body, loss of appetite, labored breathingIsolate infected fish, raise water temperature, salt baths, medication
ColumnarisBacterial infectionCotton-like formation on mouth, ragged fins, ulcers, lethargyIsolate infected fish, antibiotics, salt baths
Fin and Tail RotBacterial infectionDiscoloration, fraying of fins, shorter fins, clamped finsAddress underlying causes, antibiotics, salt baths
Fungal InfectionInfected food, poor water conditions, open woundsLoss of appetite, lethargy, frayed fins, cotton-like patchesQuarantine, antifungal medications, improved water quality
Gill FlukesPoor tank conditions, ammonia spikes, infected fish, plants, or equipmentDamaged gills, gasping for air, mucus production, scratchingIsolate affected fish, anti-fluke medications, salt baths
Camallanus WormCamallanus wormsThread-like worms from anus, abdominal bloating, loss of appetiteQuarantine, fenbendazole, levamisole, praziquantel, balanced diet
Viral Haemorrhagic Septicaemia (VHS) NovirhabdovirusLoss of appetite, erratic swimming, red spots, bulging eyesNo specific cure, antibiotics may help
Popeye (Bulging Eyes)Bacterial, fungal, or parasitic infectionsHazy bump on the eye, bulging eyes, loss of vision Isolate affected fish, antibiotic baths
ShimmiesPoor water conditions, high temperatureErratic swimming, twitching, labored breathing, clamped finsAddress water quality issues, gradual temperature adjustments, antibiotics
Wasting Disease (Skinny Disease)Internal parasites, poor diet, stress Rapid weight loss, stringy poop, damaged fins, sores, organ damageQuarantine, antibiotic treatment, balanced diet with added vitamins
DropsyOrgan failure (kidneys, liver), bacterial infections, water quality issuesSwollen belly, pinecone-like scales, bulging eyes, pale gills, stringy poopIsolate affected fish, salt baths, antibiotics, euthanasia if severe
Swim Bladder Disease:Unknown, possibly nutrition or environment-related Sunken abdomen, inability to stay upright, sinking to the bottomIsolate affected fish, salt or Epsom salt baths, surgery (in severe cases)

Quick Tip: Always quarantine new fish before adding them to your aquarium, especially if you’re unsure of their health history.

How to Breed Swordtail Fish?

Swordtail fish are known for being relatively easy to breed in a home aquarium. They have a simple breeding process compared to species that require complex spawning rituals.

1. Breeding Tank Preparation

Though not compulsory, a separate breeding tank significantly increases the chances of fry survival.

It’s better to use a breeding tank for a controlled environment to monitor the breeding process and protect the fry from potential predators.

Choose a 20-gallon tank and maintain the following conditions:

  • Water Temperature: 80 °F (27 °C)
  • pH Levels: 7.5

Add fine-leaf plants throughout the aquarium to offer hiding spots for the fry and create a conducive environment for breeding.

2. Ideal Mating Conditions

Maintain a male-to-female ratio of around 1 male to 3 or 4 females. You can keep more males in larger tanks, but it’s essential to ensure a balanced ratio. Make sure all specimens are at least 12 months old to get the best fry quality.

Mimic the rainy season in the fish’s natural habitat. Increase the water temperature and maintain higher air humidity.

Provide extra food during this period to boost their energy levels for successful mating.

3. Mating Ritual

The male swims beside the female and nips at her, which indicates that mating is about to occur. He then inseminates her internally using his gonopod.

Some females may experience sex reversal and even grow a “sword”-like structure on their tail. They may try to mate with other females, but they are usually infertile.

4. Signs of Pregnancy

A pregnant female becomes noticeably plump as she carries developing fry within her body. She also develops a dark ‘gravid’ spot near the anal fin which becomes more prominent as the pregnancy progresses.

5. Gestation Details

The gestation period for the fish can last from 4-6 weeks. The female fish are ovoviviparous or livebearers, they give birth to live fry.

It can give birth to a substantial number of fry, ranging from 100 to 300 or more, depending on factors such as the female’s size and health.

6. Fry Appearance

The newborn fry resembles miniature versions of adult fish, though much smaller in size.

7. Parental Behavior

Swordtail fish do not exhibit any parental instincts and may even attempt to eat their own offspring if they are left in the same tank.

So, you can relocate the fry to a 20-gallon tank of similar water conditions. Ensure the tank has good filtration and heating equipment. You can also isolate the female fish before giving birth in this tank. This will save you the pain of looking for and removing the fry.

Or you can provide ample hiding spots within the main tank. Live plants, particularly Java moss, offer excellent refuge for the fry and also protect them from being eaten by adult fish.

8. Feeding Fry

Swordtail fry are tiny and cannot consume standard flakes or pellets. They require special food, such as powdered fish food, small insect larvae, infusoria, or freshly hatched brine shrimp, during their initial stages of development.

In about a year, the fry will grow to its full size.

Breeding Tip: Swordtails reach sexual maturity and 8-12 months of age, but they can start breeding as early as three months old. So separate them by gender at that age unless you want a tank full of fry.

How to Buy Swordtail Fish?

  • Avoid specimens with dull skin, lethargic activity, or ragged fins.
  • Choose ones with bright coloration, active swimming behavior, a good appetite, erect fins and tail, and a plump abdomen.

A word from FishInAquarium

Swordtail fish are extremely vibrant and come in a variety of colors to match your tank’s aesthetics. They seem like a dreamy wave of color when swimming in your aquarium.

They are also super easy to breed, affordable, and readily available at most pet stores. So, you can easily get a bounty bunch of them and begin your journey.

If you liked this article, please share it with fellow aquarium enthusiasts. Don’t hesitate to mail us if you have any queries. Happy Fishkeeping!

Minnie B Miller - Professional aquarist and owner of FishInAquarium

About Minnie B Miller

Minnie B. Miller, a professional aquarist and owner of FishInAquarium, has over 8 years of expertise in fish breeding and care, gained through her roles at AquaticTX and Sea Lion Landing. Having honed her skills with various aquatic species, she is dedicated to empowering fellow enthusiasts by sharing her knowledge and experience.