Koi Tricolour Swordtail (Xiphophorus hellerii)

Koi Tricolour Swordtail (Xiphophorus hellerii)

Koi Tricolour Swordtail is a colourful domestic form of Xiphophorus hellerii, selected for koi-style orange, white and black patterning. It combines the active swimming style of a classic swordtail with the strong colour contrast of ornamental livebearer strains. Each fish can develop a slightly different balance of orange, pale and dark markings, so the gallery should be treated as representative rather than a promise of one exact pattern.

This is a medium-sized livebearer that needs more room than its juvenile shop size suggests. FishBase records wild Xiphophorus hellerii to around 14 cm total length in males and 16 cm in females, so the aquarium should be planned around an adult swordtail rather than the selected dispatch size. The current live Shopify variant is the source of truth for supplied size, price and stock.

What you are buying

• Scientific name: Xiphophorus hellerii
• Trade form: Koi Tricolour Swordtail
• Origin of species: Mexico through parts of Central America; the koi tricolour fish sold in the aquarium trade are domestic ornamental stock
• Adult planning size: allow for a substantial livebearer, with females potentially larger-bodied than males
• Temperament: active and generally community-compatible, but males can display, chase and compete
• Diet: omnivorous, taking quality dry food plus plant and invertebrate-based variety
• Water: neutral to alkaline, moderately hard to hard water
• Sale unit: one fish per quantity unless a variant explicitly states otherwise

Colour and sex

The “Koi Tricolour” name describes the domestic colour pattern, not a separate species. Orange, white and black areas can vary between individuals and can change in visual intensity as the fish grows, settles and is viewed under different lighting. A young fish may not show the same colour balance as a mature display specimen.

Adult males develop the characteristic sword-like extension to the lower part of the tail and a gonopodium, while females usually become fuller-bodied and lack the long sword extension. Small juveniles cannot always be sexed confidently. Unless the live variant specifically guarantees sex, the product should be treated as unsexed stock.

Aquarium size and layout

Use a mature aquarium with a useful horizontal swimming length. Our practical planning floor is around 110 litres or larger for a small managed group, with more room strongly preferred if keeping several males, mixing multiple livebearer species or allowing fry to remain in the tank. A longer aquarium is more useful than a narrow tall tank because swordtails are active open-water swimmers.

Provide planted or structured cover around the back and sides while keeping clear swimming lanes through the middle. Hardy stem plants, vallisneria, floating cover and pieces of smooth wood can provide retreat areas without turning the whole aquarium into dense cover. Use a secure lid because active livebearers can jump when startled or chased.

Water parameters

Xiphophorus hellerii naturally occurs in neutral to alkaline, mineral-rich water. FishBase records a broad aquarium-relevant range around 22–28°C, pH 7.0–8.0 and approximately 9–19 dH. Domestic strains may tolerate some variation, but stable hard-water conditions are generally more appropriate than very soft acidic water.

Keep ammonia and nitrite at zero in a fully cycled aquarium. Use regular partial water changes, sensible stocking and a filter with enough biological capacity for active livebearers. Swordtails feed eagerly and produce a meaningful bioload, so clear water should not be confused with low waste unless water tests confirm it.

Feeding

Koi Tricolour Swordtails are omnivores. Use a quality livebearer flake, small pellet or granule as the staple, then rotate suitable vegetable and invertebrate-based foods for variety. Spirulina-containing foods, softened vegetable matter and small frozen foods such as daphnia, brine shrimp or cyclops can all form part of a balanced routine.

Feed modest portions that are cleared promptly. In a mixed community, spread food across more than one area so smaller or lower-ranking fish are not excluded. Avoid heavy repeated feeding simply because the fish continue to beg; livebearers can become overweight and excess food quickly damages water quality.

Social behaviour

Swordtails are social, active livebearers rather than tight schooling fish. Males may display to females and to each other, and repeated chasing becomes more problematic in short or crowded aquariums. A single male with several females is a common management approach where sex is known, because it spreads courtship pressure, but that ratio cannot be promised from unsexed juvenile variants.

If keeping multiple males, provide extra space, plant cover and broken sight lines. Watch for one fish being continuously chased, prevented from feeding or forced into a corner. That is persistent social pressure rather than harmless display behaviour.

Tank mates

Choose peaceful to moderately active fish that tolerate similar neutral-to-alkaline, mineral-rich water. Other suitable livebearers, robust small rainbowfish and peaceful bottom dwellers can work in an appropriately sized aquarium when adult size and feeding competition are considered.

Avoid very small nano fish that may be intimidated, delicate long-finned species that cannot escape active courtship or chasing, and soft-water specialists whose chemistry requirements conflict with the swordtail setup. Fin-nipping species are also a poor match for adult males with extended tail swords.

Breeding and fry

Like other swordtails, Xiphophorus hellerii is a livebearer. Females give birth to free-swimming young rather than laying external eggs. In a planted community aquarium some fry may survive among dense floating or fine-leaved cover, while adults and tank mates will eat many exposed young.

Livebearers can reproduce quickly. Before intentionally keeping males and females together, have a realistic plan for fry numbers, grow-out space and rehoming. Do not buy several unsexed juveniles assuming the aquarium population will stay fixed.

Health and routine care

A healthy swordtail should swim actively, hold its fins open, feed readily and maintain a smooth body profile. Persistent clamped fins, heavy breathing, shimmying, isolation or refusal to eat should prompt an immediate check of temperature, ammonia, nitrite, nitrate and social pressure.

Hard-water livebearers often respond poorly to unstable soft water and repeated chemistry correction. Test the source water first, choose livestock that matches it where possible, and make gradual changes rather than chasing a perfect number with additives.

Before ordering

Choose Koi Tricolour Swordtails if you want an active, colourful hard-water livebearer and can provide enough swimming length, mature filtration and a plan for adult social behaviour. Reconsider if the aquarium is a small nano setup, very soft and acidic, newly cycled, or already crowded with fast livebearers.

The two current size options are dispatch-size variants, not different species or permanent adult sizes. Use the live variant selector for current supplied size, price and availability. The product title and description intentionally keep the natural search language around Koi Tricolour Swordtail, Xiphophorus hellerii, livebearer care, hard-water aquarium setup, tank mates and breeding without repeating disconnected keyword strings.