Berliner Swordtail (Xiphophorus hellerii var.)

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Berliner Swordtail
Xiphophorus hellerii var.
Berliner Swordtail (Xiphophorus hellerii var.)
Name Berliner Swordtail
Name Lat. Xiphophorus hellerii var.
Family Livebearers
Family lat. Poeciliidae
Order Killifishes & Livebearers
Order lat. Cyprinodontiformes
Origin Central America (breeding variety)
Habitat Streams, ponds
Diet Omnivore
pH 7.0-8.0
Behavior Peaceful
Keeping Group
Care Level Easy
Reproduction Livebearer
Breeding Simple
Life Span 3-5 years
Protection No
Metric Units
Size 10-12 cm
Temperature 20-28 °C
Hardness 10-25 °dH
Aquarium ~ 150 l
US Units
Size 4"-4.7"
Temperature 68-82 °F
Hardness 178-445 ppm
Aquarium ~ 40 gal

Distribution and habitat

The Berlin Swordtail is a breeding form. The natural range of the swordtails extends from the southern catchment area of the Rio Nautla in southeastern Mexico, through Guatemala and Belize to northwestern Honduras. They live mainly in shallow, flowing or stagnant waters with dense underwater vegetation.


The aquarium should have a varied, partly dense planting, with shelters and hiding places (roots) and provide sufficient swimming space. Slightly shaded light (floating plants) and medium to hard water is ideal.

No ammonia, ammonium and nitrite should be detectable, the nitrate value should not exceed 100 mg/l. To ensure the water quality and oxygen content, a filter and heater adapted to the aquarium size is required, as well as lighting for the species-appropriate day-night rhythm of the animals.


The food supply consists of dry, frozen and live food. For a balanced diet, feed once a day with a high quality dry food (flakes, granules, pellets) as well as cyclops, daphnia, artemia, mosquito larvae, etc. (live or frozen). In addition, they need plant food, such as algae leaves, algae wavers, over-broiled leafy and wild vegetables or dry food with high plant content.

It is recommended to feed small portions several times a day, which are eaten within a few minutes. A regular and varied diet promotes health and increases resistance.

Behaviour and compatibility

They are swimming, peaceful fish and well suited for a community tank. Harmless quarrels may occur among older males. It is recommended to keep at least 5 swordtails together, whereby the number of females should predominate.

Basically, only compatible fish species with similar demands on water quality and water temperature should be socialized

Sex dimorphism

Males are smaller and have an anal fin (gonopodium) that has been transformed into a mating organ. Sexually mature males bear a "sword" on the lower part of the caudal fin. Females are larger and appear rounder.

Reproduction and breeding

Swordtails are live-bearing fish. Internal fertilization is facilitated by the male's gonopodium. Fertilized females are usually clearly recognizable by a dark colored pregnancy spot on the posterior abdomen. After 4-6 weeks of gestation, up to 120 fry are born. They are already fully developed and independent at birth. After they have filled their swim bladder at the water surface, they can immediately start feeding.

Fry must be fed several times a day with special rearing food (Artemia nauplii). In community tanks breeding is hardly possible, because the fry are easy prey.


Swordtails are bred in many varieties. Mostly they are crosses with Platy (Xiphophorus maculatus) or Parrot Platy (Xiphophorus variatus)

Soft water is not tolerated well and makes them susceptible to disease. The addition of sea salt (mineral salt) from the pet store to harden the water prevents.

The well-being of the fish should be monitored regularly. Temperature should be checked daily, pH, hardness and nitrate levels should be checked at least every 14 days. Regular partial water changes are recommended, even if the contaminant level has not yet reached the upper limit. Sudden changes in water quality should be avoided. Newly introduced fish must be accustomed slowly to the water in the aquarium.

Further literature can be found in your pet store.


Text: petdata; Image: petdata 

Source: BMELV (1998): Tierschutzgutachten - Haltung von Zierfischen (Süßwasser); RIEHL & BAENSCH (2006): Aquarien Atlas Bd. 1, Mergus Verlag; ENGELMANN (2005): Zootierhaltung - Tiere in menschlicher Obhut: Fische, Verlag Harri Deutsch

  • Gemäß § 21 Abs. 5 Tierschutzgesetz idgF