Kohaku Wag Swordtail - Xiphophorus hellerii

Kohaku Wag Swordtail (Xiphophorus hellerii)

The Kohaku Wag Swordtail, Xiphophorus hellerii, is a colourful captive-bred livebearer strain combining koi-style red and white Kohaku patterning with darker “wag” fin markings. Males develop the classic swordtail extension on the lower caudal fin, while females are usually larger-bodied and lack the sword. This active, hardy freshwater fish is best suited to peaceful hard-water community aquariums with stable water quality, open swimming space and calm tank mates.

Common Name:
Kohaku Wag Swordtail, Kohaku Swordtail, Koi Wag Swordtail, Koi Swordtail, Wag Swordtail, Swordtail.

Scientific Name (Latin):
Xiphophorus hellerii
Often written in the trade as Xiphophorus helleri. Captive-bred Kohaku Wag colour form.

Maximum Size:
Males usually around 10–14 cm including the sword. Females may reach around 12–16 cm and are often fuller-bodied than males.

Water Type:
Freshwater; can tolerate slightly brackish conditions, but normally kept in freshwater aquariums.

Origin / Natural Habitat:
The Kohaku Wag form is a captive-bred ornamental strain and does not occur as a wild population. Wild Xiphophorus hellerii is native to Central America, where it inhabits freshwater and sometimes slightly brackish habitats including vegetated streams, rivers, warm springs, canals and ponds.

Water Parameters:
Temperature: 22–28°C
pH Range: 7.0–8.0
Hardness or Salinity: Moderately hard to hard freshwater preferred; avoid very soft, acidic water. Stable mineral content and regular maintenance are important for livebearer health.

Temperament:
Peaceful but active. Kohaku Wag Swordtails are suitable for community aquariums with robust, non-aggressive tank mates. Males may chase females and compete with other males, so mixed groups are best kept with more females than males where possible.

Diet:
Omnivorous. Offer quality tropical flakes, livebearer pellets, small granules, spirulina flakes, algae-based foods, frozen daphnia, brineshrimp, cyclops, bloodworm and occasional vegetable foods such as blanched courgette or spinach. A varied diet with plant matter helps support colour, digestion and condition.

Minimum Tank Size:
A minimum of 120 litres is recommended for a small group, with larger aquariums preferred. Swordtails are active swimmers and appreciate a longer aquarium with open swimming room.

Behaviour & Activity:
An active upper-to-midwater livebearer that spends much of its time swimming in open areas, browsing plants and displaying. Males use the sword-shaped tail extension during courtship and rivalry. Females give birth to free-swimming fry rather than laying eggs, and breeding can be frequent if both sexes are kept together.

Aquarium Category:
Community Fish
Suitable with peaceful hard-water community fish such as platies, mollies, larger guppies, peaceful rainbowfish, hardy tetras that tolerate alkaline water, bristlenose plecos, snails and Corydoras kept within suitable conditions. Avoid aggressive cichlids, large predators, persistent fin-nippers and very soft-water specialists.

Special Requirements or Care Notes:
Keep in a mature, well-filtered aquarium with stable hardness, stable temperature and regular water changes. Provide plants, open swimming room and a secure lid, as swordtails are active and can jump. If keeping mixed sexes, expect fry and plan stocking accordingly, as females can store sperm and produce multiple broods. Kohaku and wag markings vary naturally between individuals, so each fish may show a different balance of red, white and dark fin patterning.

Suitable for:
Beginner to intermediate fishkeepers

Availability:
Occasional in trade / Captive-bred colour form

All images are a visual representation of the fish you will receive, made to be as accurate as possible. Please note that Mother Nature is a wonderful thing, and variation in patterns and colours will occur — that is part of the unique beauty of these animals.