Short-sword platyfish

Short-sword platyfish (Xiphophorus continens) is a tiny northern swordtail from Mexico's Rio Panuco basin. Males carry only a stub of a sword and often spar, which is striking to watch in such a small livebearer. Kept cool and well-aerated, this nano fish stays active and can live 3-6 years.

Origin and natural habitat

Native to the Rio Ojo Frio in the Rio Panuco basin of northeastern Mexico, this species occupies cool, clear, oxygen-rich water. That background explains its preferences in aquariums: clean conditions, steady flow with good gas exchange, and temperatures on the cooler side for livebearers.

Aquarium setup and water conditions

Despite their size, start at 13 US gallons or larger. A larger footprint helps diffuse male-male tension and gives room for displays. Use a reliable filter that provides strong surface agitation and keep maintenance consistent to preserve water clarity.

• Temperature: 20-25 C
• pH: 7-8
• Hardness: 5-20 dGH
• Water: freshwater, clean and well-aerated

Hardscape and plants that break up sight lines help keep the peace. Combine open swimming space with patches of fine-leaved plants or moss if you want fry to survive in the display.

Diet and feeding

Omnivorous. Offer a quality flake or small pellet as the staple, plus regular feedings of small live or frozen foods. Baby brine shrimp and similar bite-sized items keep condition high and color sharp. Feed modest portions 1-2 times daily and vary the menu.

Behaviour and tankmates

Listed as semi-aggressive, mostly due to male rivalries. Males posture and chase, especially in tight quarters. Provide space and cover to diffuse line-of-sight and reduce persistent harassment.

• Best in a species-focused setup or with robust, alert fish that tolerate 20-25 C.
• Avoid slow, long-finned, or timid species that may be stressed by the activity.
• If mixing sexes, plan for fry and give females retreats. Many keepers run single-sex groups to manage numbers.

Breeding

A livebearer that produces free-swimming fry. In clean, well-oxygenated water, you can expect regular broods. Dense plant cover lets some young evade attention in the main tank; for higher yields, move heavily pregnant females to a separate, cycled rearing tank and return them after birth.

Newborns take freshly hatched baby brine shrimp and finely crushed prepared foods. Small, frequent meals and frequent small water changes grow them well.

Common problems and how to avoid them

• Overheating or low oxygen: Warm, stagnant water leads to stress. Keep temps within 20-25 C and maintain strong aeration.
• Crowding and line-of-sight: Too-tight quarters ramp up male aggression. Use a tank at least 13 gallons with plants and hardscape to break sight lines.
• Neglected maintenance: This species comes from clear water. Regular water changes and filter upkeep are key to stable pH 7-8 and moderate hardness.
• Incompatible tankmates: Avoid very slow or delicate fish and species that need higher temperatures.