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Swordtail: Vet-Approved Pictures, Size, Care, Tank Setup, & More

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By Nicole Cosgrove

swordtail fish in planted aquarium

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Dr. Luqman Javed

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Swordtails are a type of live-bearing fish that are in the same family as platys and guppies. Though the term “swordtail” is a reference to the genus Xiphophorus, most people also use the term to describe the green swordtail, Xiphophorus hellerii. However, the fish is available in several different color morphs.

Swordtails are colorful fish with interesting tail fins that make good additions to tropical freshwater aquariums. Swordtail fish get their name from their long and pointed tails fins which look like a sword. They are relatively peaceful and social fish that can be found in many vibrant colors and patterns, such as red and neon bands.

Due to the swordtail’s relative ease of keeping, they are suitable for both beginner and advanced fish keepers alike. This article will provide you with the necessary information on caring for swordtails and how you can keep them healthy.

Quick Facts About Swordtails

Species Name: Xiphophorus helleri
Family: Poeciliidae
Care Level: Easy
Temperature: 18-27°C (64.4-80.6 °F)
Temperament: Social and peaceful, but males may harass females
Color Form: Orange, red, yellow, silver, blue, white, black, among others
Lifespan: 3-5 years
Size: Males: Up to 5.5 inches (15 centimeters); Females: Up to 6.3 inches (16 centimeters)
Diet: Omnivore
Minimum Tank Size: 20 gallons
Tank Set-Up: Tropical, freshwater, or brackish water, planted
Compatibility: Social

Swordtail Fish Overview

swordtail fish in aquarium
Image Credit: slowmotiongli_Shutterstock

Swordtails, scientifically known as Xiphophorus helleri belong to the live-bearing fish family Poeciliidae. There are several different species of swordtail species in the Xiphophorus genus, most of which are kept as pets. They originate from Northern and Central America, ranging from Mexico to northern Guatemala, to Costa Rica, Belize, and northern Honduras. Swordtails inhabit various bodies of water like streams, ponds, and slow-moving rivers. They are freshwater/brackish fish that prefer warmer waters and can adapt to a very wide range of pH levels (5.5-7.8).

In the wild, swordtails will form large shoals and swim amongst dense vegetation. They make captivating pet fish with their peaceful temperaments and bright colorations. The wild populations have an olive-green coloration with yellow and red streaks across their torpedo-shaped bodies. Years of selective breeding in captivity have resulted in new varieties of swordtails with unique colorations and fin types uncommon in wild populations.

They closely resemble platyfish and are often mistaken as the same species. However, male swordtails have an elongated tail fin that makes them distinguishable between the two. They are also used in genetic and medical-related research alongside other live-bearing fish. This research allows us to get a better understanding of their reproductive strategies and carcinogenesis.

How Much Does a Swordtail Fish Cost?

Swordtails are not expensive fish. They cost between $5 to $10 on average, but their price can vary depending on their coloration and fin types. It is not uncommon for some rarer varieties of swordtails to cost up to $20 from reputable breeders. However, pet stores and many online vendors sell them for a fraction of that price.

Typical Behavior & Temperament

Swordtails have a peaceful temperament and social behaviors. They are non-aggressive and non-territorial fish that do well in community aquariums. Swordtails prefer to swim along the middle and top parts of an aquarium as they are not bottom-dwelling fish. Due to the swordtail’s social nature, they need to be kept in groups of five or more.

As the males are generally only interested in breeding with the females, a ratio of at least 1:2 is recommended, and females should be twice as numerous as males. It is better to have even more females per male (ratios of 1:5 are also considered acceptable).

Keeping swordtails alone or in pairs can stress them out and cause them to hide more than usual. When kept in appropriately sized groups, swordtails will form loose shoals and regularly interact with each other. They aren’t usually shy fish if their living conditions are ideal.

Appearance & Varieties

swordtail fish in aquarium
Image Credit: Darko Cvetanoski, Shutterstock

Through years of selective breeding, various new varieties of swordtails have been created. Out of the 19 different species of swordtails, the X. helleri is commonly kept in aquariums. Some of the captivity species are also the result of hybridization. Swordtails are medium-sized fish that grow between 3.5 to 6 inches in size, with the females being larger than the males. They have a single caudal fin with the bottom part extending to nearly half the length of their bodies in males. Swordtails can be found in many different colors and patterns. The females usually have a rounded caudal fin and do not have the sword extension like males do.

Some of the most popular color forms include orange, red, white, yellow, and black. They can have stripes, spotting, and multiple colors that provide fish keepers with plenty of variations to choose from.

Species of Swordtail:

  • Green swordtail (X. helleri)
  • Delicate swordtail (X. cortezi)
  • Panuco swordtail (X. nigrensis)
  • Chiapas swordtail (X. alvarezi)
  • Yellow swordtail (X. clemenciae)
  • Pygmy swordtail (X. pygmaeus)
  • Marbled swordtail (X. meyeri)

Varieties of Swordtail:

  • Pineapple swordtail
  • Neon green swordtail
  • Montezuma swordtail
  • Wild green swordtail
  • Berlin black swordtail
  • Koi swordfish
  • Red velvet swordtail
  • Orange swordtail
  • Dalmatian swordtail

All these varieties are in fact color morphs of X. helleri.

aquarium plant divider

How to Take Care of Swordtail Fish

Habitat, Tank Conditions, & Setup

Swordtail fish are relatively easy to care for. Let’s look below at what their care entails.

Tank Size

Swordtails require a spacious fish tank that can support their adult size and group numbers. The minimum tank size for three to five juveniles is 20 gallons. However, up to 30 gallons is usually recommended for groups larger than five. The larger the tank is, the more swordtails you can keep inside. Swordtails are not a good choice for small fish bowls or vases since they require space to swim and display their natural behaviors.

man cleaning aquarium using magnetic fish tank cleaner
Image Credit: hedgehog94, Shutterstock

Water Quality & Conditions

Water quality is important for swordtails, and they are not very tolerant of poor water conditions. Cold aquariums with high levels of ammonia can make swordtails susceptible to disease and may even contribute to a shorter lifespan. It is recommended to cycle the aquarium and keep the water heated before adding swordtails.

Temperature: 18-27°C (64.4-80.6 °F)
pH: 5.5-7.8
Water hardness: 1-15 dH


Swordtails can be kept with various substrates, such as gravel or sandy ones. They don’t have much preference when it comes to substrates. However, you want to avoid substrates with bright colors from dyes, since these substrates may leach chemicals into the water over time.


Live plants like java moss, amazon swords, and anubias are great for swordtail aquariums. They can help improve water quality and create a natural environment for your swordtails. Swordtails have plenty of vegetation in the wild, so adding some to their aquarium is recommended.


Swordtails tolerate low to moderate lighting in their aquariums. The lighting will also be beneficial for live plant growth. The lights should only be kept on during the day and turned off at night so that your swordtail can rest in total darkness.

Image Credit: BLUR LIFE 1975, Shutterstock


Like most aquarium fish, swordtails need a filter. The filter helps to aerate the water and prevent it from becoming dirty and stagnant. However, the filter should not produce a fast current since swordtails don’t enjoy swimming against strong water flow.

aquarium plant divider

Are Swordtails Good Tank Mates?

The swordtail’s peaceful and non-aggressive temperament makes them the perfect tank mates. They are rarely fin nippers and don’t seem to bother other fish in the same aquarium. You can successfully keep swordtails in community aquariums with other small peaceful fish. Invertebrates such as snails and shrimp can also be kept in the same aquarium as swordtails.

Some popular swordtail tank mates include other livebearers like mollies, platys, and guppies of the same sex. Mixed groups are not recommended, as swordtails can hybridize with fish such as platys. Peaceful tetras also do well in the same tank as swordtails. You generally want to avoid keeping them with aggressive fish like cichlids and bettas, or with temperate water fish like goldfish and koi.

red swordtail
Image Credit: Arunee Rodloy, Shutterstock

What to Feed Your Swordtail Fish

Swordtails are omnivorous and thrive on a diet of both plant and animal-based foods. Your sword’s main diet should consist of pelleted food and supplements. Their pellet-based food should be formulated for live-bearing fish and be small enough to fit in their mouths. In terms of supplements, swordtails can eat small live or frozen foods like daphnia, baby brine shrimp, and bloodworms.

You can occasionally offer swordtails spirulina or algae flakes for added variety in their diet. Swordtails should be fed once or twice a day. A generally safe guideline is to only feed as much as they can eat within 2-3 minutes. Overfeeding your swordfish may cause water quality issues and health issues.

Precise feeding guidelines require knowing the weight of your fish. This can be guessed based on their length but is generally only considered for mass production purposes (where feed costs are crucial).

Keeping Your Swordtail Fish Healthy

A healthy and well-cared-for swordtail can live for up to 5 years. There are several ways that you can keep your swordtail healthy and thriving in your care.

  • Start by providing your swordtail with a spacious aquarium. A standard rectangular tank over 20 gallons in size is recommended. Keeping your swordtail in a small aquarium is not ideal and they don’t have much room to swim comfortably.
  • As tropical fish, swordtails require a heater in their aquarium. The temperature should be within their ideal temperature range with few fluctuations. An aquarium thermometer allows you to monitor their water temperature and make any necessary adjustments.
  • Good water quality is crucial for your swordtail’s Swordtails do not tolerate traces of ammonia and nitrite in their water, so these parameters should be kept at 0 ppm.
  • Swordtails are naturally social and should be kept in groups of five or more. Keeping swordtails in groups allows them to form shoals and feel less stressed.
  • Ensuring that your swordtail is fed a healthy and balanced omnivorous diet is important. Their diet plays a role in their growth and development, so choose high-quality foods that provide them with plenty of nutrients.


Swordtails are live-bearing fish and do not lay eggs—female swordtails give live birth to fry instead. Swordtails reproduce internally and not externally like many other species of fish. Males and females can be distinguished by their size and reproductive organs. Male Swordfish have an elongated tail extension, whereas females have a rounded tail fin.

The males also have an elongated and pointed anal fin known as a gonopodium which is used for internal fertilization. Swordtails breed prolifically in the right conditions and are pregnant for around 28 to 35 days. Female swordtails can give birth to around 20 to 100 fry at a time.


Swordtails can be suitable for many aquariums if their water conditions can be met. These fish should be kept in freshwater aquariums with heated water between 18-27°C (64.4-80.6 °F). Their aquarium needs to be over 20 gallons in size to support a group of five or more swordtails.

The aquarium should ideally be planted, but you can keep swordtails in aquariums with fake plants. Although swordtails make a good choice for community aquariums, this is only if they are kept with other peaceful and non-aggressive fish. A swordtails aquarium should also contain a filtration system that doesn’t create much of a current but still aerates the water.

With proper care, you can expect your swordtails to live between 3 and 5 years on average.

Featured Image Credit: haireena, Shutterstock

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