Should I buy it?
Swordtail
Xiphophorus hellerii
Also known as: xiphophorus helleri, Xiphophorus helleri
Fishori provides conservative planning guidance, not guarantees.
Based on multiple reputable aquarium care sources with strong agreement. Use the numbers here as planning defaults — your room, water, and routine still shape real-world outcomes.
Larger livebearer with the same hard-water needs as mollies. Males push each other in cramped tanks and the species jumps.
Best for
Larger livebearer community tanks 100L+ with lateral swim space.
Avoid if
You've got a small or short tank; only soft acidic water; or want a fish that stays under 6cm.
Top things that go wrong
- Shrimp & snails. Shrimp: depends on the individual fish. Some leave them alone, others hunt cherry shrimp down within a week of meeting them.
Common mistakeTwo swordtail males in the same tank. Males establish dominance fast and the weaker one hides until it stops eating.
What most shops don't tell you
- 1.Spawning, breeding, or rearranging territory can make normally calm fish surprisingly aggressive in short tanks or with rival shapes.
- 2.Buying a single male and three females for a 60L. Adult swords need a 90 cm footprint, not a litre count alone.
- 3.Open-topped tanks. Swordtails jump and a startled male can clear an unlidded rim.
- 4.One male per tank unless the footprint is long. Multiple males harass each other. Hardy and prolific in hard tap water.
About this species
Swordtails are hard-water Central American livebearers. The male grows the sword on the lower tail and pushes other males in cramped tanks. Strong jumpers.
- Molly80L min · same group, comparable tank size
- Platy60L min · same fish family
- Endler's Livebearer40L min · same fish family
- Guppy40L min · same fish family
- Sailfin Molly120L min · same group, similar adult size
- Ghost Shrimpalso beginner semi-aggressive, similar tank size
- Kribensisalso beginner semi-aggressive, similar tank size
- Boesemani Rainbowfish tank mateslists this fish as a safe and recommended mate
- Convict cichlid tank mateslists this fish as a safe and recommended mate
- Firemouth Cichlid tank mateslists this fish as a safe and recommended mate
- Molly tank mateslists this fish as a safe and recommended mate
- Opaline gourami tank mateslists this fish among its safer mates
- Platy tank mateslists this fish as a safe and recommended mate
Plan grid
Key limits are shown above; this section adds planning detail: pH band, swim level, bioload and activity, and the radar.
Swim zones
Planning trait chart
Six indices for comparing species on paper before you spend.
- Beginner ease63
- Peacefulness44
- Community fit39
- Small-tank fit100
- Hardiness79
- Energy54
Numbers are deterministic planning indices from Fishori fields — not a scientific score of your individual fish.
Common setup sketches
Conservative patterns from Fishori fields — still run the pair checker for every species you add; sketches are not a stocking guarantee.
Avoid “one of everything” baskets — Swordtail belongs in a plan built around territory, line-of-sight breaks, and matched water chemistry.
Tank mate intelligence
Mollies, platies, larger rasboras, corydoras, peaceful gouramis. Avoid long-finned slow fish; swordtails are pushy at feeding.
Pair-level compatibility with this fish as anchor.
Read the blocking rule on each pair page before experimenting.
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: Swordtail + Platy
- Try Platy — open the pair check.
- Try Molly — open the pair check.
- Try Guppy — open the pair check.
- Try Corydoras Catfish — open the pair check.
Behaviour, temperament, and what to watch
Prose and lists come from the same record: read temperament first, then glass-level signals so you are not surprised after day three.
Peaceful in a group but rival males posture and chase in small tanks. Keep one male per tank or 4+ males in a long footprint.
Stress / aggression triggers on file
- Crowding and limited territory
- Similar-looking fish in the same tank
- Spawning, for any breeding pair
Fin nipping: Not a habitual fin-nipper, but individuals can still test fins under stress or in a crowded tank.
Predation: Not a predator toward similarly-sized community fish. The usual community caveats about mouth size still apply for very small fry or shrimp.
Territory: Holds territory on substrate, in caves, or at the surface film. Break the line of sight with hardscape, and avoid placing the tank where the fish can see its own reflection.
Planted tanks: good — easy plant ideas
In the glass: typical and warning signs
- Moderate pacing — not hyperactive, not motionless.
- Clamped fins, gasping at the surface, hiding non-stop, or refusing food after the first week.
- Rapid breathing when parameters swing — fix ammonia/nitrite first, then reassess mates.
- Chasing one individual repeatedly, torn fins on tank mates, or food theft every feed.
- Corner guarding, flaring, or body-blocking — territory is normal until it becomes relentless.
- Separate or rehome if injuries appear, one fish is pinned, or feeding becomes a daily chase.
- If water is stable but behaviour worsens, reduce stocking or remove the highest-impact species first.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Care parameters: water, food, inverts, grouping
Chemistry and group rules sit here so you are not re-reading the same line from tank mate or temperament blocks. Swim level is in the plan grid above.
Hardness
medium-hard
Diet
omnivore
Mixed diet: a quality flake or pellet as the staple, with frozen or live foods two or three times a week.
Shrimp & snails
Shrimp: depends on the individual fish. Some leave them alone, others hunt cherry shrimp down within a week of meeting them.
Kept in pairs or small groups of 3 or more. Buy them at the same time rather than adding one fish at a time.
Livebearers breed every few weeks. Plan sex ratios, a grow-out tank, or rehoming routes before the first batch of fry lands.
- Hold 20 to 28 °C steadily on a real thermometer, not the dial on the heater.
- Aim for pH 7 to 8 and a hardness you can re-test in two weeks. A one-time strip in the shop car park is not a water test.
- Footprint: short wide tanks and tall narrow tanks fish differently for the same volume. Match the tank shape to the swim pattern, not just the litre count.
- Tank volume meets or exceeds 80L published minimum for adults.
- You can stock at least 3 individuals (group welfare).
- Heater can hold 20–28°C without cooking cooler-water tank mates.
Explore and stocking hubs
Same library as the rest of Fishori: tank-mate index for this species, category peers, guides, and litre-based stocking lists where min tank on file is within the hub volume.
Plan with tools
Pair-level rules and multi-fish stocking use the same conservative engine — add this fish in the tank builder only after mates pass pair checks.
Filtration & heating
A 80L minimum tank needs a filter rated for at least 320L/hr turnover and a heater to hold 20–28°C reliably.
Plant suggestions
Swordtail does well in planted tanks. Plants compatible with 20–28°C and pH 7–8:
Profile status: verified · Evidence tier: high · 3 linked source(s). Fishori does not fabricate citations.
Fishori uses conservative planning rules based on these sources.
Confidence is explained in the summary at the top of this page (same tier as here), not repeated below.
How Fishori evaluates compatibility (same logic as pair and tank tools).
- Seriously Fish. Xiphophorus hellerii
Primary: aquarium size, water chemistry, behaviour, and compatibility (URL verified in upgrade script; recheck if site content changes).
- FishBase. Xiphophorus hellerii
Secondary: taxonomy, distribution, and maximum length in nature; cross-check with aquarium import lines and measured tank parameters.
- Wikipedia. Xiphophorus hellerii
Secondary: general species context; verify all husbandry numbers against a dedicated aquarium care sheet and your test kit, not a single table row.
Evidence notes
- The Seriously Fish profile for the binomial in this record was successfully reached as the primary aquarium reference.
- FishBase contributes natural-range size and habitat context. Translate those numbers through your heater, your water report, and your tank footprint before stocking.
- Wikipedia is only cited if the article URL returned OK. Use it for orientation, not as the only care sheet for an import.
- All compatibility text reflects typical hobby experience and the Fishori model. Individual fish, shop stress, and the order tank mates are added in can still defy a single-paragraph label.
- Fishori profiles work from typical aquarium trade sizes and hobby care norms. Specialist site checks and literature review for this species are not yet recorded here, so the ranges on this page are planning numbers rather than guarantees.