Xiphophorus hellerii
Swordtail
The swordtail is an active, hardy livebearer named for the male's sword-shaped tail. It needs a longer tank with swimming space and a cover, as it can jump.
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At a glance
- Scientific name
- Xiphophorus hellerii
- Family
- Poeciliidae
- Origin
- Mexico and Central America
- Lifespan
- 3–5 years
- Adult size
- 10–14 cm including the sword
- Weight
- 4–8 g
- Temperament
- Active, hardy livebearer; males carry the namesake sword extension on the tail.
- Activity level
- High; a strong, restless swimmer.
- Social needs
- Keep in groups with at least two females per male; males can be pushy.
- Intelligence
- Modest.
- Noise
- Silent.
Housing and environment
- Housing
- Minimum 100 litres with a secure lid — they jump.
- Space requirement
- Long community tank.
- Temperature
- 22–28 °C.
- Humidity
- Not applicable.
- Exercise
- Needs swimming length more than height.
- Grooming
- Not applicable.
Life stages and changing needs
Expanded care guidance · Updated 7 October 2026 · Not professionally reviewed
Young animals and settling in
Young livebearers are miniature free-swimming fish, not eggs attached to plants. If fry appear, provide cover and an intake guard, and check that food reaches them without fouling the water. A crowded breeding box is not a long-term nursery. Plan homes and filtration capacity before intentionally breeding; never release surplus fish into drains, ponds or waterways.
Adult care and reproductive changes
Adults may breed repeatedly, and females can produce later broods after separation from males. Watch for persistent chasing, damaged fins and fish hiding from companions. Add visual barriers and reassess stocking rather than assuming harassment is harmless. A single-sex group can avoid ongoing reproduction, but it still needs adequate space and compatibility monitoring.
Later life and changing needs
There is no reliable birthday at which these fish become senior. Follow the individual: body condition, swimming control and ability to reach food matter more than a calendar label. A fish becoming thin or inactive needs water tests and a health assessment; ageing does not explain ulcers, rapid breathing or a sudden loss of appetite.
Diet and feeding
Omnivorous flake with vegetable content plus occasional frozen foods.
Use a complete food intended for the species, with appropriate plant ingredients, rather than treating algae as a complete ration. Choose particles small enough to swallow and offer variety through suitable prepared or frozen foods. Bread, kitchen scraps and mammal meat do not provide balanced fish nutrition. Store food dry and replace stale supplies.
Feed small amounts while observing every fish, including timid individuals. Remove uneaten food and reduce the next portion if it accumulates. More food means more waste, not necessarily faster healthy growth. A change in appetite should prompt checks of temperature, ammonia, nitrite and other species-relevant water parameters before adding medications or changing multiple variables.
Daily care and ongoing checks
Every day
Each day check filter flow, heater operation where used, swimming, respiration and feeding response. Count fish and inspect for injuries. A mature biological filter is essential before stocking; clear water can still contain harmful nitrogen waste. Treat replacement water for chlorine or chloramine and avoid sudden temperature or chemistry changes.
Regular maintenance and prevention
Keep a log of water tests, partial water changes and new arrivals. Base maintenance on test results and stocking, not a fixed promise that one weekly change fits every aquarium. Preserve filter bacteria by avoiding untreated tap-water rinses of biological media. Use separate quarantine equipment and ask an aquatic vet about an appropriate quarantine plan.
Behaviour and compatibility
Breeds readily; males may squabble in small tanks.
- With children
- Good family fish.
- With other animals
- Peaceful with other robust community fish.
- Training difficulty
- Not trainable.
Health
- Ich
- Fin rot
- Stress from male harassment
A covered tank is essential; swordtails are notorious jumpers.
Special care requirements
See the housing, diet and health sections — this species has needs that are easy to underestimate.
Swimming length and escape prevention
Swordtails are active swimmers with a strong tendency to jump. A secure lid needs safe openings around equipment while maintaining the aquarium’s intended ventilation. Leave open swimming length as well as planted cover. The male’s tail extension adds visual length without meaning the fish needs less space for its body and activity.
Persistent male chasing can wear down other fish. Observe the group away from mealtimes and check for hiding, fin injury and missed food. Rearranging cover may help, but it cannot compensate for overcrowding or incompatible individuals. Have a safe, cycled separation option if an animal is being injured.
Before you take one on
Sources and further guidance
These welfare and veterinary resources inform general husbandry advice; they do not certify this profile or replace a species-experienced professional. Confirm exact environmental settings and feeding plans for your animal.
Can your home meet swordtail needs?
- Plan for a lifespan of 3–5 years, including holiday cover and, where one is available, a vet familiar with this species. Lifespan ranges are not guarantees.
- Arrange the social setting before arrival. Social guidance for this species: Keep in groups with at least two females per male; males can be pushy. Do not assume another animal of any species is a suitable companion.
- Habitat priority for this species: Long community tank. Make sure your setup can provide this consistently. Check temperature and water quality with a thermometer and test kits rather than guessing.
- Key care point: See the housing, diet and health sections — this species has needs that are easy to underestimate. Discuss diet and any specialist needs with the supplier, rescue and a vet who treats this species, and check local legal requirements before acquiring an animal.
Educational reference, not an individual diagnosis or a verified professional review. Read our editorial policy.
Guidance libraries and further reading
These organisations publish relevant guidance. Their links are further reading, not evidence that they have reviewed this page.