Swordtail Green Male
Swordtail Green Male
Another popular livebearer for the tropical freshwater community setup is the unique Swordtail. Swordtails are available in a range of colours from red to green but are most popular for the male’s extended caudal fin which takes on the appearance of a sword.

The swordtail’s body is elongated, its pelvic fins are narrow yet pointed, dorsal fins are flattened slightly and the adult male features an extended caudal fin on its lower side. Commonly they feature a pronounced lateral line however due to selective breeding this is sometimes faint.

Females are plumper in body shape and do not feature a “sword” tail. Females take on the appearance of a platy, which incidently can crossbreed with swords in the aquarium quite easily.

Common Name(s) : Swordtail

Family : Poeciliidae


Species : Xiphophorus helleri

Koi Swortail
Koi Swordtail

Origin : Central America –  Mexico, Guatemala, Honduras

PH : 6.8 – 7.5

Hardness : Moderate to Very Hard

Temperature : 22 – 28°C / 72–82°F

Maximum Size : Males – 12.5cm / 5″ Females – 8cm / 3.2″

Lifespan : 3-4 years

Aggression Level : Low (2.5/10)

Recommended Tank Size : 30 Litres +

Strata : All over


A planted tank suits the Swordtail requirements. Bunch plants like Wisteria, Blue Stricta, Green Pennywort, Purple Temple will create lots of hiding places for Swordtail fry.

To go one step further with with the breeding needs of fry, you could consider adding some Java Moss – a fast growing very bushy plant that is extremely dense and the perfect hiding place for the young baby fish. Anchor down the clump of Java Moss with a rock or driftwood.


  • Tropical Fish
  • Dwarf Cichlids


Red Swordtail
Red Swordtail

Omnivores, in the aquarium they will take a wide range of foods including flake, pellets, vegetables, bloodworm or brine shrimp.


Adult male and female Swordtails are easy to distinguish. Males feature a “sword” tail while the females do not.

For sexing juvenile fish that not yet have swords, the males also have a modified anal fin, this is called the gonopodium. This is the male sexual organ. The gonopodium has the appearance of a horizontal fin that sits below the lower side of the fish, while a female features a triangular anal fin that is set back a little.

Swordtails are livebearers and are very easy to breed. The females are almost always pregnant and will give birth to live fish every 4 to 6 weeks. Often the mother will have between 20-100 fry.

Because these fish are avid breeders, it is recommended that at least 2-3 females should be kept to each male, so the females aren’t continually harassed. Also for the same reason, a tank housing both male and female Swordtails would ideally contain plants so the females can hide from keen males.

If you wish to breed Swordtails it is recommended that a separate breeding tank be set up to separate the mother from the community tank, taking at least half of the existing community tank water. If the mother is not separated and is allowed to give birth in the community tank, more than likely the fry will not survive as the other fish (even including the mother) will eat them.

Often birthing can be induced by raising the water temperature to 28C (however personally I do not recommend stressing the fish during any stage of pregnancy if it can be avoided.) After the birthing has finished, usually after 1 to 3 hours, the mother should be removed and returned to the community tank.

Raising the fry is reasonable simple. Being reasonable in size at around 1cm from birth, they can then be fed baby brine shrimp or fine crushed flake food. Water changes are needed regularly, even daily as the fragile fry are very susceptible to water pollution.


I have encountered some boisterous males that simply will not get on in certain aquariums. This is rare but can happen – generally these are a fine addition for most small-medium tanks.

Swordtails will generally inhabit the upper third level of an aquarium – but generally they will visit all areas..

Being omnivores, Swordtails will eat a wide variety of food. Guppies will accept and do well on flake along with live and frozen foods such as brine shrimp and bloodworms. Algae is an excellent food source and should be left to grow on certain ornaments or one side of the tank, so the fish can nibble on it between meals. It is a good source of vitamins B, C, D and E.


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