Kohaku Swordtail Care Guide - Aquarium Setup, Diet & Breeding

Kohaku Swordtails are a striking cultivated form of the Green Swordtail, recognised for their koi-like red-and-white patterning. Depending on the strain, the body may show a white base with red patches across the head, back or flanks, while the fins can be clear, red or marked with matching colour. Males carry the distinctive elongated lower ray of the tail fin that gives swordtails their common name.

These are active, confident livebearers that spend much of their time in the middle and upper levels of the aquarium. They are generally peaceful, although males may display to one another and occasionally chase females, particularly in a small group or when there are too few females available.

In nature, Xiphophorus hellerii inhabits flowing streams, river margins, springs and quiet backwaters. The species is adaptable and may be found around aquatic vegetation, submerged roots and rocky edges, where it grazes on algae and searches for small food items.

Kohaku Swordtails combine the lively character of a traditional swordtail with a high-contrast ornamental colour pattern. Their active swimming and frequent livebearer breeding make them an engaging choice for a spacious community aquarium, provided their adult size and energetic nature are taken into account.

Kohaku Swordtails are a selectively bred colour variety of Xiphophorus hellerii, a species native to parts of Mexico and Central America. Wild swordtails occur in freshwater streams, rivers and associated habitats from eastern Mexico south through Guatemala and Honduras, with introduced populations established elsewhere.

A group of Kohaku Swordtails should have at least a 110-litre aquarium, with a footprint of about 90 cm long by 40 cm wide; a larger tank is preferable for multiple males or a growing population. Use a secure lid because swordtails can jump, leave open swimming space at the front and middle, and arrange hardy plants, including floating cover, around the sides and rear. A fine gravel or sand substrate, smooth stones, driftwood and good filtration create a naturalistic layout, while moderate water movement suits their riverine background. Stable, well-oxygenated water and regular maintenance are important, and a slightly alkaline, moderately hard mineral content is usually well tolerated.

Males reach about 14 cm (5.5 inches) including the extended tail sword, while females are usually larger and can reach approximately 16 cm (6.3 inches).

Offer a varied omnivorous diet based on a quality tropical flake or small pellet, supplemented with spirulina or other algae-based foods. Blanched spinach, zucchini and shelled peas can provide useful plant matter, while frozen or live daphnia, brine shrimp, bloodworm and similar foods add protein. Feed small portions once or twice daily, removing uneaten food promptly, and give growing fry finely crushed foods and baby-brine shrimp.

Kohaku Swordtails generally suit peaceful, similarly sized community fish such as platies, mollies, larger tetras, rasboras, peaceful barbs, Corydoras and smaller peaceful rainbowfish. Avoid housing them with fin-nipping species, highly aggressive cichlids or very small, delicate fish that may be harassed by their activity. Long-finned, slow-moving fish can also be vulnerable to persistent attention from males. Keep more females than males, ideally with one male for every two or three females.

Kohaku Swordtails are livebearers and breed readily in a well-maintained aquarium. Keep one male with at least two or three females to spread the male’s attention. After mating, the female can give birth to around 20–100 free-swimming fry after roughly four to six weeks. Dense floating plants, such as Java moss or guppy grass, provide shelter, although adults may eat the young. Fry can be raised on powdered flakes and suitably sized baby-brine shrimp.

Males are smaller and develop the characteristic sword-shaped extension on the lower part of the caudal fin. They also have a gonopodium, a narrow modified anal fin used for reproduction. Females lack the sword, have a normal fan-shaped anal fin and usually develop a deeper, bulkier body, especially when carrying fry.