Xiphophorus hellerii – Green Swordtail

Xiphophorus helleri or perhaps better known as the Green Swordtail is a peaceful fish species that can be kept in a community aquarium.

Xiphophorus hellerii – Green Swordtail

Xiphophorus hellerii owe their common name Swordtail to the lower extended fin rays that form the typical ‘sword’ in male fish. In addition, the males, like all other livebearers, are recognizable by their gonopodium. The females’ bodies are larger and fuller and they have a rounded tail.

In males, the sexual characteristics do not all show up at the same time. There are early males that show all sexual characteristics at 3 months of age, and late males who only show them between 10 and 18 months. The latter grow much larger and stronger than the first group and have relatively many daughters, while the first group mainly produces sons.

Although the early males remain smaller than the 2nd group, 8 centimeters excluding the sword can be considered normal. After developing the sword, early males will also continue to grow. This is not the case with late males.

Green Swordtails usually do not grow longer than 10 to 12 centimeters in the aquarium, but larger specimens have been spotted in the wild.


Mexico, Guatemala, Belize and Honduras.

The Aquarium

Green Swordtails can be kept in an aquarium of about 100 centimeters in length, but because the males need quite a lot of space for the courtship, which takes place all year round, it is better to offer them even more space. For the same reason, the aquarium should not be planted too densely, so that the fish have sufficient swimming space.

Social qualities

These fish (with a few exceptions) behave peacefully towards other aquarium inhabitants, which makes them very suitable fish for the community aquarium. In most cases, even the males get along well with each other. Since the males are very active in their attempts to mate, it is advisable to keep them with several females. They live in all water layers but have a preference for the upper water layer. Green Swordtails are very active.

It is best to keep them in a ratio of 1 male with several females or with 5 or 6 males and more females than males. If you only keep 2 or 3 males, the dominant male will continue to chase the others until they succumb to the constant chasing after a few weeks/months. In a larger group of males, attention is more divided.

Temperature and water composition

Green Swordtails do not make many demands on the quality of the water. They thrive at a water temperature around 24°C, but they also reproduce in water that is a few degrees warmer or colder.


These oviparous fish are true omnivores and they thrive on good quality dry food. Algae, fresh or in the form of dried flakes, should certainly not be missing from the menu. They also particularly enjoy eating mosquito larvae and Daphnia. Green Swordtails tend to eat their own young when they are still very small.

Breeding Xiphophorus hellerii – Green Swordtail

These strong fish are very productive. A litter contains between ten and fifty or more young fish that can immediately take care of themselves. Since Green Swordtails, but also other aquarium inhabitants, sometimes want to eat these young fish, it is wise to raise the young in a separate tank or to ensure that the aquarium offers sufficient hiding places for them, such as Java moss and many floating plants with roots. The strongest specimens will then be able to survive without any problems. For the young fish, use fine dust food (S. Micron) and also ensure that they have sufficient algae available.

Breeding forms

Over time, many different breeding forms of the Green Swordtail have emerged. The so-called ‘Green’ Swordtail is the stock form from which, among others, red, black, spotted and even yellow-orange colored fish have been bred. A particularly beautiful high-finned (‘Simpson’) and a long-finned variety are also known. The males of the latter species often have problems mating. Sometimes they cannot mate, because not only the outer fin rays of their tail fin, but also the gonopodium (reproductive organ) is greatly elongated. The albino form has become extremely rare these days.

Xiphophorus helleri - Green Swordtail - Wild variant
Xiphophorus helleri – Green Swordtail – Wild variant
Xiphophorus helleri - Green Swordtail - Orange/White breeding strain - Male
Xiphophorus helleri – Green Swordtail – Orange/White breeding strain – Male



BiancaB – Botia

Copyright images

John de Lange


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