Green Swordtail (Xiphophorus helleri)

Green Swordtail (Xiphophorus helleri) is a classic, hardy livebearer and one of the most recognizable freshwater aquarium fish. Native to Central America, it’s prized for its active behavior, ease of care, and prolific breeding.

 Overview

• Common Name: Green Swordtail
• Scientific Name: Xiphophorus helleri
• Family: Poeciliidae
• Origin: Mexico, Guatemala, Honduras
• Adult Size:
  • Males: ~10–12 cm (4–5 in) including sword
  • Females: up to ~14 cm (5.5 in)
• Lifespan: 3–5 years (often longer with excellent care)

 Identification

• Males:
  • Prominent elongated lower caudal fin ray (“sword”)
  • Slimmer body
  • Gonopodium (modified anal fin)
• Females:
  • Larger, deeper-bodied
  • Rounded tail
  • Wider, fan-shaped anal fin

Wild-type (green) coloration: Olive-green to brownish body with iridescent sheen; captive strains may show reds, blacks, pineapple, koi, or tuxedo patterns.

 Aquarium Care

Tank Size

• Minimum: 30 gallons
• Ideal: 40+ gallons for active swimming and multiple males
  Swordtails are fast, constant swimmers and benefit from horizontal space.

Water Parameters

• Temperature: 22–28 °C (72–82 °F)
• pH: 7.0–8.2 (neutral to alkaline)
• Hardness: Moderate to hard (10–30 dGH)
• Flow: Moderate
• Filtration: Strong biological filtration recommended

Swordtails tolerate a wide range but thrive in stable, alkaline, mineral-rich water.

 Aquascaping

• Dense planting along the sides and back
• Open swimming space in the center
• Hardy plants preferred:
  • Vallisneria
  • Java fern
  • Anubias
  • Sword plants (Echinodorus)
• Driftwood and smooth rocks optional

 Diet

Omnivorous with a strong plant-matter requirement.

Staple Foods

• High-quality flake or pellet with spirulina
• Vegetable-based foods

Supplemental Foods

• Blanched spinach, zucchini, peas
• Live or frozen foods: brine shrimp, daphnia, bloodworms (treats)

A veggie-rich diet helps prevent digestive issues and aggression.

 Temperament & Compatibility

• Temperament: Active, sometimes pushy but generally peaceful
• Social Structure: Best kept in groups, with more females than males

Recommended Ratio

• 1 male : 2–3 females (reduces stress and harassment)

Good Tank Mates

• Platies
• Mollies
• Guppies
• Corydoras
• Bristlenose Plecos
• Peaceful rainbowfish

Avoid

• Aggressive cichlids
• Fin-nippers (e.g., tiger barbs in small tanks)
• Very slow-moving or long-finned fish in cramped setups

Breeding

Swordtails are livebearers and breed readily.

• Gestation: ~24–35 days
• Fry per batch: 20–80+
• Breeding Difficulty: Easy

Tips

• Provide dense plant cover for fry
• Separate fry if survival rate matters
• Adults may eat newborn fry if not well-fed

Females can store sperm and produce multiple broods after a single mating.