Swordtail Fish Species Profile

Swordtail fish profile

The Spruce / Adrienne Legault

Swordtails are one of the best known beginner, community fish species, getting along with a wide variety of other fish and many different environments. They have been bred for many generations, creating many varieties within the species. Being live bearer fish, swordtails reproduce very quickly, but can be easily identified as males or females by their distinctive "sword" on the tail (caudal fin) of the males.

Species Overview

Common Name: Swordtail 

Scientific Name: Xiphophorus helleri

Adult Size: 3-4 inches

Life Expectancy: 3-5 years

Family Poeciliidae
Origin Mexico and Central America
Social Peaceful
Tank Level Top, mid-dweller
Minimum Tank Size 20 gallons
Diet Omnivore
Breeding Live-bearer
Care Easy
pH 7.0-8.5
Hardness dgH 12-30
Temperature 64 to 82 F (18 to 28 C)

Origin and Distribution

Swordtail fish have been a vibrant component of the aquarium hobbyists community for many years. Originating from Mexico and Central America, the Swordtail has been bred in captivity for countless generations. There are many varieties widely available to the aquarium community, including the naturally colored green swordtail, as well as neon, pineapple, painted, marigold wag, red wag and hi fin lyretail.

Some websites and pet stores offer "specialty" varieties that are not found anywhere else. Keep in mind that many of these unique breeds are generated through several generations of inbreeding. Although their external appearances many be very distinctive, they may also have internal issues with limited immune function and longevity.

Colors and Markings

Swordtails are named for the male's elongated ventral aspect of their tail fin, creating a "sword"-like appearance. They are bred in a wide variety of colorations. Among the varieties of swordtails, you can expect vibrant reds, yellows and blacks with a mix of bars and stripes. There are also longfin varieties of swordtails that have elongated dorsal, pectoral and tail fins to add to their eccentricity.


Swordtails do best living in a group, so plan on at least 4-5 individuals per aquarium. You are welcome to mix different varieties together, but be ready for a swarm of baby swordtails if you mix males and females. Being live-bearing fish, swordtails can reproduce very quickly, reaching sexual maturity as early as three months of age. Some potential tankmates include Neon Tetras, Coolie Loach or Corydoras.

Swordtail Habitat and Care

Swordtails do well in many different aquarium setups. These easy going fish are good for beginners and a colorful addition to any community tank. They are active fish, so make sure there are not too many decorative items in their way. The best combination for swordtails is to keep your décor and plants to the lower half to 2/3 of your tank and leave the top of the tank open for active swimming.

Male swordtails may take up territory and become aggressive towards other fish. Be sure to have plenty of room for all your swordtails, despite their small size! It may help to add fake or live plants to give your fish more hiding areas.

Swordtail Diet and Feeding

Swordtails are omnivores that enjoyed a varied diet. Depending on the water temperature, you may need to feed your fish 2-3 times per day. Many tropical fish like to forage throughout the day, so fewer feedings are not ideal for swordtails. Swordtails do well on most community micropelleted diets, and also enjoy occasional frozen and freeze-dried treats.

Gender Differences

Swordtails have specific characteristics to easily differentiate male and female fish. Males have the characteristic "sword" on the ventral aspect of their tails. Females have a rounded tail edge and tend to have thicker bodies. This comes from carrying all their live baby fry. The anal fin is also pointed in males and fan-shaped in females. This can be used to determine gender in young fish before the males develop their long sword tail.

Swordtail male and female
Swordtail male (top) and female (bottom) Flickr/Valentin Hintikka

Breeding the Swordtail

Livebearer fish, such as swordtails, can easily over populate an aquarium. Many beginners are not aware of the swordtail's livebearing abilities and are suddenly surprised by a swarm of baby swordtails. Many swordtail owners start with just a few swordtails, not realizing that the females may be pregnant when acquired. Even one pregnant swordtail may surprise a novice fish owner with a sudden population explosion.

Swordtails can become mature as early as 3 months old and birth up to 50 fry per spawning. If you don't want more baby swordtails, it is critical that you separate males from females before they reach reproductive maturity. As previously noted, males have the distinctive "sword" on the ventral aspect of their tail fin, and an elongated anal fin, making the identification easy.

Over several generations, you may note an increase in your fry deaths, or your fish may not live as long. If you continue to breed the same populations, you can expect to have health issues resulting from inbreeding . The best fix for this is adding a little genetic diversity through the purchase of new fish or trading with another hobbyist. Unless you know your new fishes' health history, before adding them to your aquarium it is always recommended to quarantine your new fish yourself.

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