Species · Livebearers
Swordtail
Xiphophorus hellerii
The livebearer with a sword — active, hardy and colourful, but bigger and jumpier than people expect. Give it space, hard water, and a tight-fitting lid.
Difficulty: Beginner Tropical community tank ✓ Fact-checked care guide
Quick facts
| Adult size | ~12–14 cm / 5–6 in (males have the long tail "sword") |
|---|---|
| Minimum tank | ~90 L / 24 US gal — SeriouslyFish recommends a 120 × 30 cm base |
| Temperature | 22–26 °C / 72–79 °F (wide range 16–28 °C / 61–82 °F — tolerates cooler) |
| pH | 7.0–8.0 (neutral to alkaline) |
| Hardness | 10–25 dGH (hard water) |
| Filtration & flow | Cycled, moderate filtration; keep a tight lid (accomplished jumpers) |
| Diet | Omnivore — quality flake/pellet plus vegetables and small live/frozen |
| Social | Keep a group; with mixed sexes keep 2–3 females per male |
| Temperament | Active and generally peaceful; males can squabble |
| Lifespan | 3–5 years |
Overview
The swordtail (Xiphophorus hellerii) is the classic active livebearer, the male trailing the long tail "sword" that gives it its name. Hardy, colourful and full of energy, it comes in countless bred varieties.
The catch is size and behaviour: swordtails get bigger (to ~14 cm) and more active than most people expect, the males can squabble, and they are notorious jumpers.
💷 Costing it out? See how much a swordtail really costs to keep — the swordtail itself is usually the cheapest part.
Water & tank
A hard-water fish: pH 7.0–8.0 and 10–25 dGH suit it. It tolerates a wide temperature range and even cooler rooms, but 22–26 °C / 72–79 °F is a good target.
Because they are large and active, give them room and length — at least ~90 L / 24 US gal (SeriouslyFish recommends a 120 × 30 cm base) — and, crucially, a tight-fitting lid, as they jump.
Feeding
An omnivore that grazes plant matter in the wild — a quality flake/pellet base plus vegetables and small live/frozen foods. Feed modestly once or twice a day.
Behaviour & tankmates
Active and generally peaceful, best with other robust, hard-water community fish. Keep 2–3 females per male (males can harass females and each other); a single-sex group avoids fry.
A livebearer — mixed groups breed readily. It also hybridises with platies, so keep that in mind.
What to expect
Constant, confident swimming and the occasional dash — and, unfortunately, a leap for any open gap, so keep the tank covered. Mixed groups will produce fry.
Myths, kindly busted
“Swordtails are small starter livebearers like guppies.”
They reach 12–14 cm, are very active, and need a large, long tank with a lid — a bigger commitment than a guppy or platy.
“A lid is optional.”
Swordtails are accomplished jumpers — an open tank loses fish. Keep it covered.
🐟 Did you know? — Swordtail fun facts
Little true delights about the swordtail — each one checked against a named source, no pet-shop myths.
- The name Xiphophorus means “sword-bearer” in Greek, for the long blade-like extension trailing from the lower tail lobe of adult males. SeriouslyFish
- A female swordtail can store a male's sperm for months, letting her keep producing broods long after mating. SeriouslyFish
- Swordtails are prized in science, including biomedical research into the genetics and causes of cancer. SeriouslyFish
When to act
We triage, not diagnose — but these are worth a closer look (starting with a water test):
- A missing fish — check the floor; swordtails jump. Cover any gaps.
- Clamped fins, lethargy or the "shimmies" — test the water and check hardness; they dislike soft, poor water.
Heading to a vet? Print the Swordtail vet-prep sheet — what to bring, what to tell them, and the questions to ask.
Sources & further reading
- SeriouslyFish — Xiphophorus hellerii — Adult ~140 mm SL; recommended 120 × 30 cm base (large tank); temperature 16–28 °C / 61–82 °F; pH 7.0–8.0; hardness 10–25 dGH (hard); active livebearer, jumper; hybridises with platies.
Written & fact-checked by The Finfern Team against the sources above — kind, general guidance, not a diagnosis. If something looks wrong, test your water and, if it persists, contact a fish-savvy vet.
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The essentials at a glance, a setup checklist and a first-30-days plan for your swordtail — what to get right and what to watch for. Join the shoal and we’ll send it over. Free sheets and tools always stay open, no gatekeeping.
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