Neon Swordtail (Xiphophorus hellerii var.)

The Neon Swordtail is a selectively bred color variety of Xiphophorus hellerii (the Green Swordtail), native to the Atlantic slope drainages of eastern Mexico and Central America. The 'Neon' designation refers to the intense blue-teal to electric blue iridescence that has been bred into this variety, creating a more vivid, metallic blue coloration compared to the natural green-red wild type.

Male Neon Swordtails display the characteristic elongated lower caudal fin extension — the 'sword' — typically blue or blue-black in coloration, complementing the electric blue body. Some variants are combined with a 'wag' pattern where all fins are dark or black, creating strong contrast with the neon blue body. Females lack the sword and are generally less colorful, though they may show traces of blue iridescence on the flanks.

Swordtails are prolific livebearers — females give birth to 20–100+ fully formed fry per brood after a 4–6 week gestation period. Male swordtails may sometimes spontaneously change sex to female (sex reversal), particularly if raised in female-dominated groups — a phenomenon common in Xiphophorus species.

Neon Swordtails share the hardiness and adaptability of all Swordtail varieties, making them ideal for beginners while offering the dramatic coloration appreciated by experienced fishkeepers.

Neon Swordtails thrive in moderately hard, neutral to slightly alkaline water: pH 7.0–8.5, hardness 10–25 dGH, and temperatures 22–28°C. They adapt to a range of conditions but prefer harder, alkaline water reflecting their Central American origins.

A minimum 80-liter aquarium with horizontal swimming space suits a small group. Dense plantings provide cover for females and fry. Good filtration and moderate current are beneficial. A tight lid is recommended — swordtails are capable jumpers.

Feed quality flake food, pellets, vegetable flakes, spirulina, daphnia, brine shrimp, and bloodworms. A varied diet with plant-based components enhances the neon coloration and general health.

Males may be aggressive toward females and occasionally with each other. Maintain at least 2–3 females per male to distribute breeding pressure. Compatible with other livebearers, corydoras, medium tetras, barbs, and most peaceful community fish. Avoid nippy species that target the elongated sword fin.

Breeding is prolific. Dense plantings or a separate breeding tank allow fry survival. Regular water changes of 25–30% weekly maintain water quality.