Swordtail

The swordtail (Xiphophorus hellerii) is a freshwater fish. It belongs to the genus Cyprinodontiformes . The swordtail is a member of the family of live-bearing tooth carps (Poeciliinae). Its home is Central America. The swordtail is also known by other names:

  • Spotted swordtail
  • Helleri
  • Oaxaca swordtails
  • Brass sword carrier
  • Striped swordtail carrier (green swordtail)

What distinguishes swordsmen?

The attitude of swordtails is uncomplicated. The unusual appearance comes from the lower tail fin. This narrow extension measures one third of the body length. The sword-like appearance of this caudal fin gives this ornamental fish its name.

The appearance of swordtails

Swordtails have an elongated body and a pointed head. The colours vary in wild and cultivated forms. Wild catches have a body height between 14 cm and 16 cm. The ground colour is brown-green and shimmers metallically. The stripes on the flanks are brown, black or red.

The number of stripes varies depending on the species. Furthermore the swordtails have spots on the caudal fins. The sword is yellow and bordered with black and in older animals partly completely black. The first breeding form was a cross between Platy and swordtails. The offsprings show strong colour variations, for example orange or red.

The sword is bordered with black at the edges. The breeding form remains smaller. The body height varies between 10 cm and 12 cm. The swordtails have a life expectancy of up to 5 years.

Keeping conditions

This ornamental fish, which loves to swim, is easy to keep. In addition, a group of at least 5 fish should be kept. For the well-being some points must be considered:

  • Fresh water
  • Minimum length aquarium 100 cm (160 l)
  • Cover on the aquarium
  • close planting
  • Caves made of wood or stone
  • Water temperature between 22 °C and 28 °C
  • pH value between 6,5 and 8,5
  • Total water hardness between 10 and 30 °dGH

Gender differences

With the swordtail the males are clearly smaller than the females. In addition, only males have the sword-shaped appendage and the anal fin is transformed into a mating organ (gonopodium). The body of the females is more compact and they have a black spot (pregnancy spot) on the anus area.

Water values for swordtails

The swordtail is insensitive to the properties of water. There are no health problems if the basic requirements are met.

  • Water temperature: 22 °C – 28 °C
  • pH value: 6.5 – 8.5
  • Water hardness: 10 – 30 °dGH

Food and nutrition of the swordtails

Swordtails are omnivores. With a varied diet one should pay attention to a high proportion of plants and algae. Besides dry food, green and live food should also be given. With adult animals a daily feeding is sufficient. During the course of the year, one can include a fasting period. This is possible for swordtails without any problems and the owner can go on a one or two week holiday without a guilty conscience.

Feeding suggestions:

The ideal aquarium for swordtails

The fast and nimble swimmer needs sufficient space. The pool should not be less than 100 cm long. The pool water should have a slight to strong current. The male swordtails can be aggressive towards his sex mates. Therefore it is important that the aquarium has a lid so that no fish can jump out of the tank. Sufficient hiding places must also be available. A dense green planting at the edge and roots and stones at the bottom provide sufficient hiding places.

Special features of swordtails

After the birth one can optically recognize only female swordtails. Only later the sexual characteristics develop. Among the swordtails there are two types of males. These are divided into early males and late males. In the early males the sword develops relatively soon and they remain smaller and more delicate. The late males look like females for a long time. Only after longer living together with sexually mature females the sword develops. The sword becomes longer than in the early males and the late males are larger than the other males.

>> Read on: Swordtail breeding and rearing

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