rm
Passport
- Family
- Swordtails
- Grows to
- 14 cm (5.5")
- Lives
- 3–5 years
- TemperamentSuggested
- Peaceful
- Care
- Beginner
- Swims
- Mid-water
- Keep
- In a group of 3 or more
- Water
- 16–28 °C (61–82 °F)
MexicoHonduras
Care requirements
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On record for Swordtail: adult size, lifespan, minimum tank, temperature, ph, hardness, minimum group, diet, care level, swim level, tank length.
A figure that is not on record is left out rather than guessed. One marked Suggested comes from keeping knowledge rather than a page.
- Minimum tank 76 L / 20.0 US gal
- pH 7–8
- Hardness 10–25 dGH
- Diet omnivore
- Tank length 91 cm minimum
Care notes written from general aquarium knowledge, not from the cited sources.
About
Swordtails are the largest of the common livebearers and the most athletic. The male carries the lower lobe of his tail drawn out into a long point — the sword — and he uses it in display, backing and shimmying in front of females with it held rigid.
They're closely related to platies and hybridise with them freely, which is why so many shop fish look like something between the two. Reds, greens, pineapples, wagtails and lyretails are all the same animal selected differently.
They're also famous for something they rarely do: a female changing into a functional male. It happens, it's genuinely documented, and it's much rarer than aquarium folklore suggests — most "sex changes" are late-maturing males that were sold as females.
Tank setup
Give your swordtails length. They're powerful, fast fish that cover ground, and a short tank leaves them pacing.
Cover the tank properly. Swordtails jump, they jump well, and this is the commonest way people lose them.
Give them hard, alkaline water. Like all the Central American livebearers they do badly in soft acidic conditions.
Keep one male, or several with plenty of space and more females. Males spar with each other persistently and a dominant one will harry a rival relentlessly in close quarters.
Plant the sides and leave open water in the middle.
Feeding
Swordtails are omnivores that lean vegetarian, like their platy relatives.
Feed a spirulina or vegetable-based flake as the base, with blanched vegetables and algae wafers. They graze, and a diet with no plant content causes them problems.
Add protein for condition — daphnia, bloodworm, brine shrimp — as a secondary part of the diet rather than the whole of it.
Avoid: overfeeding on protein, and avoid assuming their size means they need richer food than a platy.
Filtration and flow
Moderate to good flow. They're strong swimmers and they use a current.
Filter well for a fish this size kept in a group.
Mineral content and fresh water are what keep them right. As with every livebearer here, those two between them head off most of the trouble.
With plants
Swordtails are safe with plants and graze algae from them without damage, provided they're fed enough greens.
Their size and speed mean loose plants get knocked about, so anchor stems properly.
Dense planting at the edges gives fry somewhere to survive and gives harried females somewhere to rest.
Health
They're hardy and robust in hard water, and prone to the same shimmying and fungal problems as mollies when kept too soft or too cold.
Jumping is the practical hazard. A covered tank solves it entirely.
Watch a female being pursued constantly. Sustained harassment wears livebearer females down and it's a housing problem rather than a medical one.
Breeding
Swordtails are livebearers that breed readily and produce large broods of well-developed fry.
Females store sperm and deliver successive broods from a single mating, so an apparently lone female will keep producing fry for months.
The fry are big enough to take crushed flake and baby brine shrimp immediately, and they're fast. Adults hunt them, so dense planting or a separate rearing tank decides how many survive.
Tank mates
Avoid8
- Least Killifish Swordtail grows to 14 cm against Least Killifish at 2 cm, big enough to eat it.
- Scarlet Badis Swordtail grows to 14 cm against Scarlet Badis at 2 cm, big enough to eat it.
- Common Goldfish Common Goldfish is not safe with Swordtail: common goldfish and swordtails are a bad pairing.
- Demasoni Cichlid Demasoni Cichlid is not safe with Swordtail: african cichlids and swordtails are a bad pairing.
- Electric Yellow Lab Swordtail and Electric Yellow Lab do not mix: african cichlids and swordtails are a bad pairing.
Only with care10
- Chinese Algae Eater Chinese Algae Eater is aggressive and Swordtail is peaceful.
- Convict Cichlid Convict Cichlid is aggressive and Swordtail is peaceful.
- Jewel Cichlid Jewel Cichlid is aggressive and Swordtail is peaceful.
- Agassiz's Dwarf Cichlid Swordtail is a risk to Agassiz's Dwarf Cichlid: sth american cichlids - dwarf and swordtails are a pairing to watch.
- Bolivian Ram Swordtail and Bolivian Ram are an uneasy mix: sth american cichlids - dwarf and swordtails are a pairing to watch.
No conflict is recorded with the other 88 species in the database, so nothing to flag. 2 species are not covered at all, so they could not be judged either way.