Koi swordtail
Xiphophorus hellerii
A colorful and active freshwater livebearer bred to resemble Koi carp with orange, white, and black mottled patterns, highly suited for community tanks.
Wassertemperatur
22 - 28 °C
pH-Wert
7 - 8.5
Wassertyp
Süßwasser / Brackwasser
Tankfüllstand
Oberfläche und Mitte
Erwachsenengröße
12 cm
Mindesttankvolumen
>= 100 L
Mindestgruppe
>= 4
GH
12 - 30 dGH
KH
6 - 15 dKH
TDS
240 - 600 ppm
Leitfähigkeit
375 - 938 uS/cm
Artbeschreibung
Geographical Origin and Habitat: The Koi swordtail is a domestic color variety selectively bred in captivity. Its wild ancestor, Xiphophorus hellerii, is native to Central America, stretching from Mexico through Guatemala, Belize, and Honduras. In nature, they inhabit fast-flowing rivers, streams, canals, and warm springs, usually preferring areas with thick marginal vegetation.
Taxonomy and Morphology: A member of the family Poeciliidae, it displays the classic elongated, stream-lined shape of swordtails. Males are easily recognized by the long extension of the lower caudal fin rays, known as the 'sword'. Females are typically larger and rounder. They grow to an average length of 8 to 12 centimeters (3 to 5 inches), excluding the male's sword.
Social Behavior: Very active, lively, and peaceful, making them ideal community fish. Males are competitive and will establish a pecking order, chasing each other and soliciting females. To avoid stress on the females, they should be kept in a harem ratio of at least two to three females per male.
Coloration and Sexual Dimorphism: The 'Koi' variant exhibits a tricolor mottled pattern consisting of white, vibrant orange/red, and black blotches. Sexual dimorphism is distinct: males possess the long caudal sword and a gonopodium (modified anal fin used for mating), while females lack the sword and have a normal fan-shaped anal fin.
Pflege, Zucht und Mitbewohner
Aquarium Setup: Provide a tank of at least 20 gallons (80 liters) to accommodate their active swimming behavior. The tank should be decorated with dense plantings of hardy species like Vallisneria, along with floating plants to provide cover for fry, while leaving plenty of open space for swimming. A secure lid is essential.
Diet and Feeding: Omnivorous with a high requirement for plant matter. They will readily eat high-quality flakes, pellets, frozen foods (like daphnia, brine shrimp, and bloodworms), and algae. Regular feedings of spirulina flakes or blanched vegetables help prevent digestive issues.
Water Quality: They thrive in hard, alkaline water conditions. The water temperature should be maintained between 22 and 28 °C (72 to 82 °F), with a pH range of 7.2 to 8.2 and a water hardness (GH) of 10 to 25 dGH. They are sensitive to sudden drops in temperature.
Compatibility and Cohabitation: Excellent tankmates for other peaceful community fish, including mollies, platies, guppies, tetras, corydoras catfish, and peaceful barbs. Avoid housing them with aggressive fish or fin-nippers, which may target the male's long tail extension.
Aquarium Breeding: Breeding is exceptionally easy, as they are livebearers. After a gestation period of 28 to 35 days, the female gives birth to free-swimming fry. To protect the fry from being eaten by the parents and tankmates, use spawning boxes or provide dense mats of floating mosses and hornwort.
Risks and Diseases: While hardy, they are susceptible to common freshwater diseases such as ich (white spot disease), fin rot, and mouth fungus under poor water quality. Regular partial water changes and proper filtration are key to keeping them healthy.
Geografische Herkunft und Verbreitung
The Koi swordtail is a domestic color variety selectively bred in captivity. Its wild ancestor, Xiphophorus hellerii, is native to Central America, stretching from Mexico through Guatemala, Belize, and Honduras. In nature, they inhabit fast-flowing rivers, streams, canals, and warm springs, usually preferring areas with thick marginal vegetation.
Ursprung
Selektive Züchtung und SortenMittelamerika und KaribikNordamerikaOstasienTropische Ozeane und Riffe
Fischprofil
- Temperament
- Territorial
- Overall, they possess an active, curious, and largely peaceful temperament suitable for many community aquariums. While generally tolerant of other species, males are known to exhibit territorial behavior and aggression toward rival males of their own kind. They are constantly in motion, exploring their environment and interacting with their surroundings. Their energetic nature adds a lot of movement to the tank, but it means they should not be housed with shy or easily stressed tankmates.
- Diät
- Omnivore
- As omnivores, they readily accept a wide variety of commercially prepared flakes, pellets, and freeze-dried foods. Their diet should be regularly supplemented with live or frozen foods such as daphnia, bloodworms, and brine shrimp to ensure optimal health and coloration. Plant-based matter is also essential, so providing spirulina flakes or blanched vegetables will help meet their nutritional needs. A varied diet ensures strong immune system function and vibrant, healthy growth.
- Lebenserwartung
- 3-5 years
- Erwachsenengröße
- 12 cm
- Geschlechterverhältnis
- Specific M:F ratio
- To maintain a harmonious aquarium environment, a sex ratio of one male to at least two or three females is strongly recommended. Males possess a strong mating drive and will relentlessly pursue females, which can lead to severe stress and exhaustion if the ratio is imbalanced. Having multiple females helps to disperse this constant attention and ensures no single female is overly harassed. Keeping multiple males in the same tank often leads to aggressive territorial disputes unless the aquarium is exceptionally large and heavily planted.
- Fütterungsfrequenz
- Twice daily
- Adults should typically be fed one to two times daily, offering only as much food as they can completely consume within two to three minutes. Overfeeding should be strictly avoided to prevent water quality deterioration and health issues like obesity or swim bladder disorders. Fry and juveniles require more frequent feedings, ideally three to four times a day with appropriately sized foods. Fasting them for one day a week can also help clear their digestive tracts and mimic natural feeding cycles.
- Bioload
- Medium
- This species has a moderate bioload that is proportional to its active swimming nature and relatively large adult size. As active foragers and regular eaters, they produce a consistent amount of waste that necessitates robust mechanical and biological filtration. Frequent water changes are highly recommended to prevent the buildup of nitrates and other harmful organic compounds. Care should be taken not to overstock the aquarium, as their waste production can quickly overwhelm a marginally filtered system.
- Fluss
- Stagnant
- They prefer moderate water flow that provides adequate oxygenation without creating an overpowering current. In the wild, they inhabit flowing streams and rivers, so a steady, gentle current mimics their natural environment and encourages active swimming. A high-quality canister filter or hang-on-back filter usually provides the ideal amount of water movement and surface agitation. Excessively strong flow should be avoided, as it can cause exhaustion and stress, particularly for long-finned varieties.
- Sprungrisiko
- Yes
- These fish are notorious jumpers and possess a strong instinct to leap out of the water when startled or stressed. A tight-fitting aquarium lid or a secure cover glass is absolutely essential to prevent them from jumping to their deaths. Care should be taken during maintenance or feeding, as sudden movements or changes in lighting can trigger this jumping behavior. Floating plants can also be used to provide a sense of security and deter them from attempting to jump.
- Reproduktion
- Oviparous
- They are prolific livebearers, meaning the females give birth to fully formed, free-swimming fry rather than laying eggs. Males possess a modified anal fin called a gonopodium, which is used to internally fertilize the females. A single mating can result in multiple batches of fry over several months, as females can store sperm. If the fry are to be raised, providing dense vegetation or using a breeding box is necessary to protect them from being eaten by the adults.
- Kompatibilität & Tankkameraden
- Harem only
- They are generally peaceful community fish, but males can display pronounced aggression and territoriality toward one another. It is best to keep them in a ratio of one male to several females to disperse any harassment and reduce stress. They do well with other similarly sized, active, and peaceful community species like tetras, corydoras, and larger rasboras. Avoid keeping them with very long-finned or slow-moving fish that might be prone to fin-nipping, or with species small enough to be eaten.
- Tankfüllstand
- Top/Middle
- They are highly active fish that utilize all levels of the aquarium, frequently swimming from the bottom to the surface in search of food. However, they tend to spend the majority of their time in the middle and upper levels of the water column. Providing plenty of open swimming space in these areas is crucial to accommodate their energetic nature. They also appreciate access to the surface for occasional feeding, but will explore the substrate when scavenging for leftover food.
Wissenschaftliche Modelle & Parameter
FishBase
Zugang zu den offiziellen wissenschaftlichen Daten der Art
FishBase v25.04Daten synchronisiert am: 15.06.2026
- Trophäenniveau
- 3,2 ± 0,43 se
- Belastbarkeit
- Hoch (weniger als 15 Monate)
- Phylogenetische Einzigartigkeit (PD50)
- 0.5
- Bayessche Längen-Gewichts-Beziehung
- a = 0.01, b = 3.06
- AnfälligkeitGeringe Anfälligkeit (10 / 100)
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