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.
Swordtail At a Glance
Swordtail Tank Requirements
Will Swordtail fit in your tank?
Care guides tell you what Swordtail needs, the next question is whether your tank can safely provide it. Test Swordtail against your tank size, maintenance needs, and the fish you already keep before you buy.
Swordtail Water Parameters
Swordtail Temperament & Compatibility
Swordtail 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.
Who Swordtail Is Actually For
Swordtail is best for a fishkeeper who wants a species that can settle into a calmer community setup and can provide a keeper who can commit to a proper group of at least 3. It makes the most sense for a hobbyist who will actually build around its needs, especially plants.
The most common mistake is buying Swordtail for looks first and only later discovering how its adult size, behavior, or bioload changes the whole tank plan. Another frequent problem is underestimating its social needs. A token pair or trio often behaves very differently from a real group.
Swordtail 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.
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Guidarium Editorial Desk
Reviewed against Guidarium care, stocking, and compatibility standards. Read the editorial policy.
- Last reviewed
- April 28, 2026
- Last updated
- April 28, 2026
- Issues or corrections?
- Contact the editorial team
Top Tank Mates for Swordtail
These fish are strong compatibility matches for Swordtail based on water preferences, temperament, adult size, and tank behavior.
White Cheeked Goby
Rhinogobius duospilus
Ideal Tank MatesTandanus Catfish
Tandanus tandanus
Ideal Tank MatesPetricola Catfish
Synodontis petricola
Ideal Tank MatesHillstream Loach
Beaufortia leveretti
Ideal Tank MatesHi Fin Peppered Cory
Scleromystax macropterus
Ideal Tank MatesAngelicus Botia
Botia kubotai
Ideal Tank MatesPlants That Suit Swordtail
These plants pair well with Swordtail based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
Afzel's Anubias
Anubias afzelii
Amazon Sword
Echinodorus amazonicus
Anacharis
Egeria densa
Anubias Barteri
Anubias barteri
Baby Tears
Lindernia rotundifolia
Balansae
Cryptocoryne crispatula
Fish Similar to Swordtail
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Northern Mountain Swordtail
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