A popular, highly active livebearer known for the male's elongated lower tail fin (the 'sword'). They are hardy but require larger tanks than other common livebearers (like Guppies or Platies) due to their size and immense swimming energy. They require hard, alkaline water and do best with a ratio of one male to multiple females to disperse harassment.
At a Glance
Tank Requirements
Water Parameters
Temperament & Compatibility
Available Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Male
Features the iconic 'sword' tail extension and a modified anal fin (gonopodium). Males are relentless in their pursuit of females and highly territorial toward other males. Multiple males should only be kept in very large tanks (150L+) to avoid fatal bullying.
Differs in 3 traits from base species
Also known as: Male Swordtail, Sword
Female
Larger, thicker-bodied than males, and lacking the sword tail. They give birth to live young roughly every 28 days and will actively eat their own fry if not provided with dense plant cover.
Differs in 2 traits from base species
Also known as: Female Swordtail
Lyretail / Hi-Fin Morph
Selective breeding has produced varieties with massively extended dorsal and tail fins. Due to the drag from their fins, they prefer slightly less current and are slower swimmers.
Differs in 3 traits from base species
Also known as: Lyretail Swordtail, High Fin Swordtail, Longfin
Swordtail Care Guide Summary
The Swordtail, scientifically known as Xiphophorus hellerii, belongs to the Livebearers family group. Adults reach a maximum size of approximately 12 cm and have a fusiform body shape with a fast growth rate. Classified as mostly peaceful, this species primarily occupies the surface and mid-level zones of the aquarium and produces a high level of biological waste.
To thrive, the Swordtail requires a brackish tolerant aquarium with a minimum volume of 110 litres and a tank length of at least 80 cm. Water temperature should be maintained between 21°C and 28°C, with a pH range of 7–8.3 and a general hardness of 12–30 dGH. A moderate water flow is preferred.
The Swordtail is a rewarding species to keep, provided its core environmental needs are met. This species is available in 3 varieties: Male, Female, and Lyretail / Hi-Fin Morph. Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
Swordtail Habitat Setup
When setting up an aquarium for the Swordtail, a moderate water flow best suits their natural preferences. Because this species occupies the surface and mid-level zones, the aquarium layout should prioritise adequate surface area with floating cover to make them feel secure near the waterline and open swimming space in the centre of the tank for free movement. Useful additions include dense planting to provide cover, break sightlines, and reduce stress. Keepers should note that a tight-fitting lid is essential, as this species is a known jumper.
Swordtail Compatibility Notes
Classified as mostly peaceful, the Swordtail is a social species that requires the company of its own kind to thrive. When choosing tankmates, their energetic swimming style may stress more sedentary or timid species. Selecting tankmates that favour different water layers from the surface and mid-level zones can help reduce competition and territorial overlap.
Frequently Asked Questions About Swordtail
How big does Swordtail get?+
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Similar Species
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Guppy
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Platy
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