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
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Water Parameters
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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
Top Tank Mates
Ghost Shrimp
Palaemonetes paludosus
🟢Ideal Tank MatesMexican Dwarf Crayfish (CPO)
Cambarellus patzcuarensis
🟢Ideal Tank MatesFiddler Crab (Brackish)
Uca sp.
🟢Ideal Tank MatesAssassin Snail
Clea helena
🟢Ideal Tank MatesBristlenose Pleco
Ancistrus cirrhosus
🟢Ideal Tank MatesReticulated Hillstream Loach
Sewellia lineolata
🟢Ideal Tank MatesSwordtail 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. An aquarium test kit can help you monitor these values.
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.
Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for Swordtail.
30 Gallon Breeder
40 Gallon Breeder
55 Gallon Standard
60 Gallon Breeder
75 Gallon Standard
90 Gallon Standard
Show 12 more tank sizes
Frequently Asked Questions About Swordtail
How big does Swordtail get?
Swordtail (Xiphophorus hellerii) typically reaches a maximum adult size of approximately 12 cm. They have a fusiform body shape and a fast growth rate.
What tank size does Swordtail need?
A minimum aquarium volume of 110 litres and a tank length of at least 80 cm are recommended for Swordtail. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does Swordtail need?
Swordtail thrives in brackish tolerant conditions with a temperature range of 21–28°C, a pH between 7 and 8.3, and a general hardness of 12–30 dGH. A moderate water flow is preferred.
Is Swordtail peaceful or aggressive?
Swordtail is classified as mostly peaceful with an aggression score of 4 out of 10. They are generally well-suited to peaceful community tanks.
Can Swordtail live alone?
No, Swordtail should be kept in groups of at least 3 to reduce stress and encourage natural behaviour.
Does Swordtail have any special tank requirements?
Yes. Swordtail benefits from plants - densely covered in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Does Swordtail need a lid on the tank?
Yes. Swordtail is a known jumper, and a tight-fitting lid or cover is essential to prevent escape. Even a small gap can be enough for a determined fish to leap out.
Similar Species
Wrestling Halfbeak
Dermogenys pusilla
A unique, surface-dwelling livebearer known for its elongated, pike-like lower jaw. Males are famous for 'wrestling' by locking jaws to establish dominance. They are strictly top-dwellers and excellent jumpers, requiring a tight-fitting lid to prevent escapes and snout injuries. They prefer hard, alkaline water and thrive in both freshwater and slightly brackish conditions.
Serpae Tetra
Hyphessobrycon eques
A striking, deep-red schooling fish known for its highly active nature. While hardy and beautiful, Serpae Tetras are notorious fin-nippers. This behavior is usually localized within their own pecking order if kept in large enough schools (8+), but they should never be housed with slow-moving or long-finned tank mates like Bettas, Angelfish, or Gouramis.
Endler's Livebearer
Poecilia wingei
A tiny, vibrant, and highly active livebearer closely related to the Guppy. Males display intense, neon colors and patterns, while females are larger and plainly colored. They are prolific breeders and require hard, alkaline water to thrive.
Molly (Sailfin/Black/Dalmatian)
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Mollies are active, hardy livebearers native to the Americas. They are famous for their ability to adapt to fresh, brackish, and even full marine water. They are voracious eaters (including algae) and produce a high bioload for their size. Note: 'Molly' covers several species; the Short-finned (*P. sphenops*) and the much larger Sailfin (*P. latipinna* and *P. velifera*).
Mosquitofish (Gambusia)
Gambusia affinis
An extremely hardy livebearer historically introduced worldwide for mosquito control. In the aquarium, they are notorious fin-nippers and highly aggressive towards other small fish. They are best kept in species-only setups or indoor/outdoor ponds. Males are significantly smaller than females.
Rainbow Shark
Epalzeorhynchos frenatum
A popular, active freshwater 'shark' (actually a cyprinid) known for its striking red fins contrasting with a dark or albino body. They are highly territorial bottom-dwellers. Only keep one per tank, as they are notoriously aggressive toward their own kind, other 'sharks' (like the Red Tail Shark), and similar-looking bottom feeders.