Description
Threadfin Rainbowfish (Iriatherina werneri)
📌 Basic Info
Scientific Name: Iriatherina werneri
Common Names: Threadfin Rainbow, Featherfin Rainbowfish, Werner’s Rainbowfish
Family: Melanotaeniidae (Rainbowfishes)
Order: Atheriniformes
Origin: Northern Australia, New Guinea, and parts of Indonesia (slow-flowing creeks and billabongs)
Size: Up to 2 inches (5 cm)
Lifespan: 3 – 5 years
Tank Zone: Upper and mid levels
🌊 Water Parameters
TDS: 100 – 250 ppm
pH: 6.0 – 7.5
Temperature: 24 – 30 °C (75 – 86 °F)
Hardness: 4 – 12 dGH
🐟 Characteristics
Body: Slender, translucent-silver body with shimmering pastel hues.
Males: Long, delicate thread-like extensions on the dorsal, anal, and caudal fins — intensely colored in red, yellow, or black.
Females: Smaller and less vividly colored.
Nature: Peaceful but delicate; prefers calm water and a gentle flow.
Display: Males perform beautiful fin-flaring displays to attract females.
🍽️ Food
Type: Omnivorous (micro-predator)
Diet: Fine crushed flakes, micro-pellets, and live or frozen foods such as baby brine shrimp, daphnia, cyclops, or microworms.
Feeding Frequency: 2–3 small meals daily.
Tip: Provide small-sized foods only — they have tiny mouths.
🛠️ Maintenance
Tank Size: Minimum 20 gallons (75 L) for a small group.
Filtration: Gentle sponge or slow-flow filter; strong currents damage their fins.
Decor: Dense fine-leaved plants (Java moss, Cabomba, Hornwort) and open swimming areas.
Lighting: Soft to moderate; enhances color and reduces stress.
Water Change: 20–25 % weekly with stable temperature and chemistry.
👥 Social Behavior
Group Size: Keep 8 – 10 or more for natural schooling and displaying.
Tank Mates: Peaceful nano fish — Neon Tetras, Rasboras, small Corydoras, Endlers, and Dwarf Gouramis.
Avoid: Fin-nippers or boisterous species (Barbs, larger Rainbowfish, aggressive Bettas).
✅ Do’s
Maintain soft, warm, and clean water.
Keep in planted tanks with calm flow.
Feed a varied, fine diet for color and fin health.
Keep in groups with more females than males.
❌ Don’ts
Don’t expose to strong currents or aggressive fish.
Don’t keep in newly cycled or unstable tanks.
Don’t use rough decorations that may tear fins.
⭐ Quick Tips
The Threadfin Rainbowfish is a graceful, delicate nano rainbow prized for its long, feather-like fins and shimmering body.
Best suited for peaceful, well-planted community aquariums, it thrives in soft, warm, calm water and groups.
A stunning choice for aquascaped or biotope setups where elegance and gentle motion are desired.
