Threadfin Rainbowfish

The Threadfin Rainbowfish is one of the most delicate and beautiful rainbowfish species available to aquarists. Native to Australia and New Guinea, these tiny fish are famous for the incredibly long, flowing filaments that extend from their dorsal and anal fins, creating a thread-like appearance that gives them their name. Males display these spectacular fins and iridescent silver bodies with hints of red, yellow, and blue during courtship displays. Despite their tiny size of less than 2 inches, they are active swimmers that constantly move throughout the water column. Threadfin Rainbowfish are peaceful, schooling fish that must be kept in groups to feel secure and exhibit their best colors. Their delicate fins make them vulnerable to fin-nipping tank mates, so careful selection of companions is essential. Their ethereal beauty and graceful swimming make them a prized addition to small planted tanks for aquarists who can provide appropriate care.

Care Requirements

Tank Setup

Threadfin Rainbowfish need a planted aquarium of 20 gallons with gentle water flow. Dense planting provides security while open areas allow for their active swimming and courtship displays. Use soft, acidic water with dark substrate to enhance their colors. Gentle filtration such as sponge filters prevents damage to their delicate fins. Dim lighting or floating plants create ideal conditions.

Water Quality

• Temperature: 75-82°F (24-28°C)
• pH: 6.0-7.5
• Water Hardness: Soft to moderate, 2-12 dGH
• Ammonia/Nitrite: 0 ppm
• Nitrate: <15 ppm

Feeding

These small fish require appropriately sized foods. Offer micro pellets, small frozen foods, and live foods like baby brine shrimp and daphnia. They may have difficulty competing with larger, faster tank mates for food. Feed small amounts multiple times daily. Their small stomachs require frequent, small feedings.

Behavior & Compatibility

Threadfin Rainbowfish are peaceful schooling fish that must be kept in groups of 8-10 or more. Their long, delicate fins are targets for fin nippers, so choose tank mates carefully. They are suitable for peaceful community tanks with other small, non-aggressive species. Males display their spectacular fins during courtship to attract females.

Tips for Success

• Keep in large groups of 10+ for best coloration and schooling behavior
• Their delicate fins are vulnerable; avoid any fin-nipping tank mates
• Males display incredible fin extensions during courtship
• Use gentle filtration; strong currents can damage their long fins
• Excellent for small planted tanks with other peaceful micro fish
• Regular small water changes help maintain pristine conditions
• Dim lighting and tannins from driftwood enhance their subtle colors