Threadfin Rainbowfish Complete Care Guide: Iriatherina werneri
The threadfin rainbowfish is the freshwater equivalent of a nano-reef fish — tiny, delicate, jewel-toned, and demanding of stable parameters most beginners cannot deliver. Males flare sail-like dorsal and anal fins with trailing filaments that can double body length, and the courtship display is one of the most elegant sights in the hobby. This threadfin rainbowfish complete care guide from Gensou Aquascaping at 5 Everton Park covers Iriatherina werneri housing, water chemistry, feeding and tank mate choices for Singapore hobbyists attempting this underrated species.
Species Profile and Origin
Native to slow-moving, vegetation-choked streams of northern Australia, Papua New Guinea and the Aru Islands, Iriatherina werneri is the sole species in its genus. Adults reach 3-4cm body length excluding filaments, making them one of the smallest rainbowfish in the hobby. Males sport red, yellow and electric blue highlights; females are silvery with shorter fins. Wild specimens live in soft-to-medium water — unusual for rainbowfish — which expands their tank mate options.
Tank Size and Layout
A 60cm planted tank of 60-80 litres suits a group of 8-10 threadfins. Length trumps height because males display laterally across open swim lanes between plant stands. Leave a clear midwater corridor roughly 30cm long where males can spar without catching filaments on stems. Dense planting along the back and sides protects females from relentless courtship. Pair with a gentle sponge filter or low-flow internal from the filtration range — threadfins struggle in strong current.
Water Parameters
Target 24-28°C, pH 5.5-7.5, GH 3-12, KH 2-6. Unlike boesemani rainbows, threadfins tolerate Singapore tap water once dechlorinated — GH 2-4 works with careful acclimation. Ammonia and nitrite must read zero; nitrate below 15 ppm. Threadfins are sensitive to organic waste and sudden parameter swings, so a mature tank (8+ weeks cycled) is non-negotiable. Weekly 20% water changes with conditioner-dosed PUB water keep the shoal stable.
Sourcing in Singapore
Threadfin rainbows rotate irregularly through Polyart, Y618 and Nature Pet at SGD 6-12 per fish. Carousell breeders occasionally list captive-bred Singapore groups at SGD 8-10 — these are dramatically healthier than Indonesian imports, which often arrive parasitised or already fin-damaged. Inspect for clamped fins, white spots or stringy faeces before buying. Quarantine for 14 days in a separate 20-litre tank with gentle sponge filtration before adding to the display.
Feeding Tiny Mouths
Threadfins take only the smallest particles. Crushed micro flakes, baby brine shrimp, micro-worms, cyclops and frozen daphnia all suit. Avoid standard tropical flakes — the pieces are too large and sink before the fish can grab them. Feed twice daily in modest amounts. During conditioning for spawning, boost live food to 60% of the diet. Stock feeding staples like Hikari Micro Wafers and frozen bloodworm for variety.
Community Compatibility
Only the gentlest tank mates work. Chili rasboras, green neon tetras, pygmy corydoras (Corydoras pygmaeus), sparkling gourami and Amano shrimp form a peaceful community at 25-26°C. Avoid anything boisterous — tiger barbs, zebra danios and honey gouramis stress threadfins within days. Larger rainbowfish of the same family outcompete them at feeding time. Betta males flare at the trailing filaments; female bettas in sororities sometimes coexist but remain a gamble.
Planting for Display and Cover
Threadfins inhabit vegetated shallows in the wild. Replicate this with Cryptocoryne wendtii clumps, Vallisneria at the back, Hygrophila polysperma stems and a floating layer of Salvinia or Amazon frogbit. Filtered light through floating plants triggers male colouration; bright overhead LEDs wash the reds out. Source plants from the live plants catalogue or pick rhizomes at C328 for SGD 4-8 per portion.
Breeding Threadfin Rainbows
Males drive females into plant thickets to spawn in java moss or spawning mops. Eggs are adhesive and hatch in 7-10 days. Adults do not actively predate eggs but will eat fry given the chance. Move a spawning mop to a separate 10-litre tank and feed fry on infusoria for the first week, then microworms, then baby brine. Raising threadfin fry is challenging — survival rates of 30-40% are considered good. Patient breeders sell groups on Carousell at SGD 5-8 per juvenile.
Common Health Issues
Bacterial infections from shipping stress are the most common early problem. Watch for fin rot on filaments, cloudy eyes or rapid gill movement. Treat with an aquarium-safe antibacterial like Seachem KanaPlex dosed at manufacturer strength. Ich appears if temperature crashes during a heavy monsoon downpour — a preventive heater set to 26°C stabilises things even in Singapore’s tropical climate. Long-term, threadfins live 3-4 years in a well-maintained tank.
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Still Have Questions About Your Tank?
Drop by Gensou Aquascaping — most walk-in questions get answered in under 10 minutes by someone who has set up hundreds of tanks.
5 Everton Park #01-34B, Singapore 080005 · Open daily 11am – 8pm
