Swordtail Fish (Xiphophorus hellerii): Care Guide


Swordtail fish (Xiphophorus hellerii) are fascinating creatures known for the long, pointed tail extension of the males, which resembles a sword, giving them their common name. Native to North and Central America, these freshwater fish inhabit a variety of environments, including rivers, streams, and warm springs. They exhibit a wide range of colors and patterns, thanks to selective breeding, including red, green, and black varieties. 

Swordtails are livebearers, meaning the females give birth to fully formed, free-swimming young, rather than laying eggs. This reproductive strategy contributes to their popularity among aquarists, as it allows for the easy rearing of offspring. 

Additionally, swordtails are known for their peaceful nature and compatibility with a wide range of tank mates, making them excellent choices for community aquariums. 

Common Name(s)Swordtail Fish
Scientific NameXiphophorus hellerii
OriginNative to North and Central America, particularly from Mexico to Honduras.
TemperaturePrefers warmer water, typically between 72°F and 79°F (22°C to 26°C).
SizeCan grow up to 5-6 inches (12-15 cm) in length, with females generally larger than males.
Minimum Tank SizeRecommended minimum tank size of 20 gallons (75 liters) for a small group.
Food & DietOmnivorous. Diet should include a variety of flake, live, and vegetable-based foods.
LifespanCan live up to 5 years in well-maintained aquarium conditions.
Water pHPrefers slightly alkaline water, with a pH range of 7.0 to 8.2.
Tank MatesPeaceful with most species but can be fin nippers; best kept with similarly sized peaceful fish.
BreedingLivebearers. Breeding is relatively easy, often requiring no special intervention in good conditions.
Common DiseasesProne to common freshwater ailments such as fin rot, ich, and velvet if water quality is poor.

Swordtail Care

Swordtails are known for their hardiness and ease of care, making them an excellent choice for both novice and experienced aquarists. They thrive in a wide range of water conditions, preferring temperatures between 72°F and 79°F (22°C to 26°C) and a pH level of 7.0 to 8.3. 

Swordtails are adaptable fish that can do well in both community tanks and species-specific setups, as long as they have plenty of space to swim and hide. They require a varied diet, consisting of high-quality flake food, brine shrimp, and vegetable matter to keep them healthy. Regular water changes and a well-maintained tank are essential to prevent disease and keep these vibrant fish thriving.

Food & Diet

Proper diet is important for the well-being of Swordtails. Here’s an overview of the best practices for their diet and feeding:

Variety is Key

  • Omnivorous Diet: Swordtail fish are omnivores, requiring a mix of plant-based and protein-rich foods to stay healthy.
  • Commercial Foods: High-quality flake foods or pellets designed for tropical fish can form the basis of their diet, providing balanced nutrition.
  • Live and Frozen Foods: Supplement with live or frozen foods like brine shrimp, bloodworms, and daphnia for protein.
  • Vegetables: Incorporate blanched vegetables such as zucchini, lettuce, or spinach to provide necessary fibers.

Feeding Schedule

  • Frequency: Feed adult swordtails 1-2 times a day. Juveniles require more frequent feeding, up to 3 times a day.
  • Portion Size: Offer only what they can consume in a few minutes to avoid overfeeding and water quality issues.

Nutritional Needs

  • Protein: Essential for growth and repair, especially for young, growing swordtails.
  • Fiber: Helps in digestion. Vegetables provide a good source.
  • Vitamins and Minerals: Commercial foods are usually fortified with essential vitamins and minerals. Variety ensures a balanced intake.

Other Considerations

It’s important to avoid overfeeding as it can lead to water pollution and health problems like obesity and fatty liver disease.

Watch your swordtails as they eat to gauge their health and happiness. Healthy swordtails are eager eaters. Changes in appetite can indicate health issues or stress, requiring attention to their environment or health.

Temperature & Water Parameters

Swordtails are relatively hardy fish that can thrive in a variety of conditions, but like all aquatic pets, they do best when their environment closely matches their natural habitat. Here are the ideal temperature and water parameters for swordtail fish:


  • Ideal Range: 72°F to 79°F (22°C to 26°C)
  • Swordtails are tropical fish, so they require warm water to stay healthy. Temperatures outside this range can stress the fish, leading to health issues or decreased activity.

pH Level

  • Ideal Range: 7.0 to 8.2
  • Swordtails can tolerate a wide range of pH levels but prefer slightly alkaline water. Consistency in pH is more important than matching the exact ideal value.

General Hardness (GH)

  • Ideal Range: 12 to 30 dGH (degrees of General Hardness)
  • They thrive in moderately hard to hard water. This mimics the mineral content of their natural habitat in Central America.

Carbonate Hardness (KH)

  • Ideal Range: 3 to 12 dKH (degrees of Carbonate Hardness)
  • A stable carbonate hardness helps prevent pH swings, which can be harmful to fish.

Ammonia (NH3)

  • Ideal Level: 0 ppm (parts per million)
  • Ammonia is toxic to fish, even at low levels. It’s important to have a well-cycled tank to convert ammonia to less harmful substances.

Nitrite (NO2)

  • Ideal Level: 0 ppm
  • Like ammonia, nitrite is toxic and should not be detectable in a well-established aquarium.

Nitrate (NO3)

  • Ideal Range: Less than 20 ppm
  • Nitrates are less harmful than ammonia or nitrite, but high levels can cause stress and health problems for fish. Regular water changes can help keep nitrate levels in check.

Water Changes

Regular water changes are crucial for maintaining the water quality within these parameters. A typical recommendation is to change 20% to 25% of the water every 2 weeks, but this can vary based on tank size, filtration efficiency, and fish load.

Additional Notes

Swordtails are adaptable fish that can tolerate a range of conditions, but sudden changes in water parameters can be stressful and harmful.

Regular testing of water parameters is important to ensure the health and well-being of your swordtails.

By maintaining these water conditions, you will create a healthy and stress-free environment for your swordtail fish, promoting vibrant colors, active behavior, and longevity.

Tank Setup

Setting up a tank for Swordtails requires attention to several key aspects to ensure a healthy and thriving environment for these vibrant and active fish. Here’s a comprehensive guide to get you started:

Tank Size

A 20-gallon tank is the minimum recommended size for swordtails, as it provides ample space for swimming and a group of these fish. If you plan to keep a larger group or include other species, consider a larger tank to prevent overcrowding and reduce stress.

Filtration and Water Movement

Swordtails thrive in well-oxygenated water with moderate movement. Use a reliable filter that does not create excessively strong currents, as swordtails enjoy both swimming in currents and having calmer areas in the tank.

Regular maintenance, including partial water changes (20-25% weekly) and filter cleaning, is essential to keep the water quality high and nitrates low.


Standard aquarium lighting is suitable for swordtails. They do not require special lighting conditions, but if you have live plants in the aquarium, ensure the lighting meets the plants’ needs.

Aquascaping and Decor

  • Plants: Live or artificial plants provide hiding spots and reduce stress. Swordtails enjoy densely planted areas as well as open swimming spaces.
  • Substrate: A gravel or sand substrate is suitable. Choose a color and texture that complements the tank’s aesthetic and the fish’s colors.
  • Decor: Include decorations such as rocks, driftwood, and caves to mimic natural habitats and provide additional hiding spaces.

Monitoring and Maintenance

Regularly test the water for ammonia, nitrite, nitrate, pH, and temperature to ensure stable conditions.

Keep an eye on fish health and behavior for any signs of stress or disease.

By following these guidelines, you can create a healthy and visually appealing environment for your Swordtail fish, allowing them to showcase their vibrant colors and lively personalities.


In general, Swordtails are known for their peaceful nature. They are active swimmers and exhibit interesting behaviors that can add dynamism to a tank. Here are some key points about their temperament:

  • Social Behavior: Swordtail fish are generally peaceful and can coexist with a wide variety of other fish species. They are schooling fish, so they thrive in groups, which helps reduce stress and promotes natural behavior.
  • Territorial Males: Male swordtails can be somewhat territorial, especially towards other males. This is more pronounced in confined spaces. To minimize aggression, it’s advisable to keep them in a spacious tank with plenty of hiding spots and to maintain a higher female-to-male ratio, such as three females for every male.
  • Compatibility: They are well-suited for community tanks that house other peaceful fish of similar size. However, their long, flowing tails can sometimes attract fin-nipping from other species, so tank mates should be chosen carefully.
  • Activity Level: Swordtails are known for being very active and enjoy spaces to swim freely. They also tend to explore different levels of the aquarium but often stay in the middle or upper parts of the tank.
  • Environmental Influence on Behavior: The environment can significantly influence their behavior. A well-decorated tank with plants, rocks, and hiding places can help mimic their natural habitat, reducing stress and promoting healthy social interactions.

For anyone considering adding swordtail fish to their aquarium, it’s essential to provide them with an appropriate environment and select tank mates carefully to ensure a harmonious community tank.

Tank Mates

Swordtails are generally peaceful, making them suitable for community tanks, but their tank mates should be chosen with care to ensure compatibility. Here’s a guide on suitable tank mates for Swordtail fish:

  • Tetras: Small, peaceful fish like Neon Tetras or Cardinal Tetras can be good companions. They are not aggressive and thrive in similar water conditions.
  • Danios: Zebra Danios or Pearl Danios are active and can coexist with Swordtails. Their speed and agility help them avoid any potential nipping from Swordtails.
  • Mollies and Platies: Both belong to the same family as Swordtails and share similar care requirements. They are peaceful and can share a tank without issues.
  • Corydoras Catfish: These bottom dwellers are peaceful and can help keep the tank clean by eating leftover food. They usually stay out of the Swordtails’ way.
  • Guppies: Although guppies are generally peaceful, care should be taken if you mix male Swordtails with male Guppies due to potential aggression over territory and females.
  • Loaches: Species like the Kuhli Loach are peaceful and occupy the bottom of the tank, complementing the mid to top-level swimming Swordtails.
  • Rasboras: Harlequin Rasboras or other small Rasboras species are peaceful, schooling fish that can share space with Swordtails.
  • Angelfish: With caution, Angelfish can be compatible with Swordtails. However, their size and semi-aggressive nature mean they’re better suited for larger tanks where Swordtails have room to escape if necessary.
  • Bristlenose Plecos: These are peaceful algae eaters that can share a tank with Swordtails. They keep to themselves and help clean the tank.
  • Dwarf Gouramis: They are generally peaceful but can become territorial. A larger tank with plenty of hiding spots can mitigate potential issues.

When choosing tank mates for Swordtail fish, consider the following factors to ensure a harmonious community aquarium:

  • Water Parameters: Ensure all species have similar requirements for temperature, pH, and water hardness.
  • Temperament: Choose species that are similarly peaceful and unlikely to bully or be bullied by Swordtails.
  • Size and Diet: Ensure that all inhabitants are of compatible sizes and have no special dietary requirements that could complicate feeding.

Always monitor new introductions to the tank closely for the first few weeks to ensure compatibility and adjust as necessary.

Common Disease & Health Issues

Like all aquarium fish, Swordtails are susceptible to certain health issues and diseases. Common health problems for swordtail fish include:

  • Ichthyophthirius Multifiliis (Ich or White Spot Disease): This is a parasitic infection characterized by white spots on the skin, gills, and fins. Fish may show signs of distress such as rubbing against objects to relieve itching, rapid gill movement, and lethargy. Treatment involves increasing tank temperature to speed up the parasite’s life cycle and using medication specifically designed to treat Ich.
  • Fin and Tail Rot: This bacterial infection causes the edges of the fins and tail to appear frayed or disintegrated. Poor water quality and stress can make swordtails more susceptible to this condition. Treatment involves improving water quality, reducing stressors, and administering antibiotics.
  • Velvet Disease (Oodinium): Caused by dinoflagellate parasites, this disease presents as a dusty, gold or rust-colored film on the fish’s body. Fish may scratch against objects due to irritation. Treatment includes using copper-based medications and improving water quality.
  • Columnaris (Cotton Wool Disease): This bacterial infection manifests as white or grayish patches on the skin, mouth, and fins, resembling cotton wool. It can progress rapidly and is often fatal. Treatment involves antibiotics and improving water conditions.
  • Bacterial Infections: Symptoms can vary but often include ulcers, sores, and red streaks on the body or fins. Bacterial infections are typically treated with antibiotics and by improving water quality.
  • Swim Bladder Disease: This condition affects the fish’s ability to regulate buoyancy, resulting in difficulty swimming normally. Causes can include overfeeding, constipation, or bacterial infection. Treatment often involves fasting the fish for a few days, providing peas to help clear blockages, and ensuring clean water conditions.

Preventive measures include regular water changes, maintaining proper water parameters (temperature, pH, hardness), avoiding overcrowding, providing a balanced diet, and quarantining new fish before adding them to an established tank. Regular observation of fish behavior and appearance can help detect health issues early, allowing for prompt treatment.


Breeding Swordtails can be a rewarding experience for aquarium enthusiasts. Here’s a basic guide on how to breed them successfully:

Setting Up the Breeding Tank

  • Tank Size: A breeding tank should be at least 20 gallons to provide ample space for the fish to exhibit natural behaviors and for the fry to grow.
  • Water Conditions: Maintain the water temperature between 72°F and 79°F (22°C-26°C) with a pH level around 7.0 to 8.3. Swordtails prefer slightly alkaline water.
  • Filtration and Aeration: Use a sponge filter to keep the water clean while ensuring the safety of fry, as they can be sucked into more powerful filters.
  • Plants and Hiding Spots: Include live plants and hiding places to mimic natural habitats and provide shelter for the fry.

Selecting Breeding Stock

  • Healthy Adults: Choose healthy, vibrant adults with strong genetic traits you wish to pass on. Typically, breeders select males with long, attractive swords and females with robust body shapes.
  • Sex Ratio: Maintain a ratio of one male to every two to three females to reduce stress and aggression from the males.

Breeding Process

  • Conditioning: Feed the breeding stock high-quality food, such as live or frozen brine shrimp, daphnia, and quality flake food, to encourage spawning.
  • Spawning: Swordtails are livebearers, meaning the females give birth to free-swimming fry. The gestation period lasts about 28 days.
  • Isolation: Once you notice a female is pregnant (evident by a swollen belly and the appearance of a gravid spot near the anal vent), you may choose to move her to a separate birthing tank to protect the fry from being eaten.

Caring for Fry

  • Feeding: Feed the fry small foods like infusoria, liquid fry food, or finely crushed flake food multiple times a day.
  • Growth: As the fry grow, you can gradually offer them larger foods, such as baby brine shrimp.
  • Water Quality: Maintain high water quality with regular partial water changes, being careful not to harm the fry.


  • Swordtails are prolific breeders, so be prepared for many fry.
  • Genetic diversity is important. Avoid inbreeding by introducing new stock occasionally.
  • Monitor water parameters closely, as fry are sensitive to poor water conditions.

By following these guidelines, you should be able to successfully breed Swordtail fish and enjoy the process of raising the fry. Breeding these fish not only adds to the enjoyment of aquarium keeping but also provides an opportunity to learn more about the fascinating world of aquatic life.

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