Threadfin rainbowfish care
Iriatherina werneri · Swamps and weedy streams of northern Australia and New Guinea
Threadfin rainbowfish are tiny rainbowfish whose males carry long, thread-like fin extensions, which they flare at each other.
- Tank size
- 20 US gal or larger
- Temperature
- 73 to 84 °F (23 to 29 °C)
- Group size
- 6 or more
- Temperament
- Peaceful
- Adult size
- 2 in (without the long tail)
- pH
- 6 to 7
- Hardness (GH)
- 2 to 12 dGH
- Lifespan
- 3 to 4 years
- Diet
- Micropredator
- Care level
- Moderate
In a 20 gallon long
30¼ × 12½ × 12¾ in outsideHow to keep threadfin rainbowfish
Threadfin rainbowfish are tiny rainbowfish whose males carry long, thread-like fin extensions, which they flare at each other. Keep six or more in a 20 gallon or larger planted tank (30 gallons is better) at 73 to 84 °F, only with small, peaceful fish that leave the threads alone.
Diet: Micropredator: fine flakes, baby brine shrimp, small frozen foods. Fish food types compared · how often to feed.
Where they swim: Middle of the tank.
Threadfin rainbowfish tank mates
Share the temperature and water, and neither side eats, nips or bullies the other. Check the full group in the stocking checker.
Honey gourami
2 in · 10+ gal · 72–82 °F
Panda corydoras
2 in · 15+ gal · 68–77 °F
Otocinclus
2 in · 20+ gal · 72–79 °F
Amano shrimp
2 in · 10+ gal · 68–80 °F
Bandit corydoras
1.9 in · 20+ gal · 72–79 °F
Bloodfin tetra
2.2 in · 20+ gal · 65–82 °F
Golden dwarf cichlid
2.2 in · 20+ gal · 72–80 °F
Agassiz's dwarf cichlid
1.7 in · 20+ gal · 75–84 °F
Keep apart
Silvertip tetra: Silvertip tetras nip long fins like those of threadfin rainbowfish.
White cloud mountain minnow: No shared temperature: threadfin rainbowfish need 73 to 84 °F, white cloud mountain minnows 64 to 72 °F.
Tiger barb: Tiger barbs nip long fins like those of threadfin rainbowfish.
American flagfish: American flagfish nip long fins like those of threadfin rainbowfish.
Pea puffer: Pea puffers belong in a tank of their own.
Amazon puffer: Amazon puffers nip long fins like those of threadfin rainbowfish.
What a threadfin rainbowfish tank needs
A tank of 20 US gallons or more (such as the 20 gallon long) with a tight lid (they jump), and the equipment below.
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Aquarium Co-Op Easy Flow Sponge Filter, Small
A sponge filter gives gentle flow and cannot pull in small fish. It runs from an air pump, with airline tubing and a check valve, all sold separately.
Aqueon PRO QuietFlow Power Filter 10
Rated by the maker for up to 20 US gal, which covers a 20 gallon threadfin rainbowfish tank without being built for a far bigger one.
Aqueon QuietFlow Internal Power Filter 15–30 gal
Rated by the maker for 15–30 US gal, which covers a 20 gallon threadfin rainbowfish tank without being built for a far bigger one.
hygger Precise Aquarium Heater 100W
Threadfin rainbowfish need 73 to 84 °F; most homes run cooler, so a heater holds the temperature.
API Freshwater Master Test Kit
Tests ammonia, nitrite, nitrate and pH, the readings that matter most before and after adding threadfin rainbowfish.
Seachem Prime 100 mL
Removes chlorine and chloramine from tap water at every water change.
Fluval Edge Thermometer
Shows the water temperature at a glance, so you know it stays within 73 to 84 °F.
More choices, each with the reason it is in or out: Filters for a 20 gallon tank · Heaters for a 20 gallon tank. We don’t list fish food: any good brand of the foods under Diet will do. Plan the whole tank's equipment →
Common threadfin rainbowfish problems
- Fin nippers such as tiger barbs or serpae tetras shred the threads.
- Their mouths are small and they eat slowly; fast fish take the food first.
Test the water first whenever fish look unwell: see what your readings mean, then match the symptom. For disease, a vet who treats fish can diagnose it and advise treatment.
More to compare
Sources
Name, origin and adult size checked against Wikipedia: Iriatherina werneri. Temperature, pH, hardness, group size, lifespan and minimum tank size are common hobby guidance, not figures from that article. Ranges are the range the species tolerates; aim for the middle. Minimum tank sizes are for an adult group. Drawings are our own; photo credits follow.
Photo credits
Real photographs from Wikimedia Commons, resized and cropped to fit; each is used under the license named.
- Threadfin rainbowfish NRJMelvinT, CC BY-SA 4.0, via Wikimedia Commons
- Honey gourami Antoon Dommerholt (Dutch Wikipedia), CC BY-SA 3.0, via Wikimedia Commons
- Panda corydoras Chronotopian, CC BY-SA 3.0, via Wikimedia Commons
- Otocinclus CHUCAO, CC BY-SA 3.0, via Wikimedia Commons
- Amano shrimp Stefanie Leuker, CC0, via Wikimedia Commons
- Bandit corydoras Gonzalo Valenzuela, CC BY-SA 2.0, via Wikimedia Commons
- Bloodfin tetra VGW2006, Public domain, via Wikimedia Commons
- Golden dwarf cichlid Borkowski.robert, CC BY-SA 4.0, via Wikimedia Commons
- Agassiz's dwarf cichlid Cisamarc, CC BY-SA 3.0, via Wikimedia Commons
- Silvertip tetra Filtropat; cropped by Kyknos, CC BY-SA 3.0, via Wikimedia Commons
- White cloud mountain minnow Petrtyl, CC BY 4.0, via Wikimedia Commons
- Tiger barb Faucon, CC BY-SA 2.5, via Wikimedia Commons
- American flagfish nat_t (iNaturalist), CC0, via Wikimedia Commons
- Pea puffer Beta Mahatvaraj, CC BY-SA 4.0, via Wikimedia Commons
- Amazon puffer O. Schneider, CC BY-SA 3.0, via Wikimedia Commons
- Boesemani rainbowfish H. Zell, CC BY-SA 3.0, via Wikimedia Commons
- Dwarf neon rainbowfish Leo-nie-weh-oh; cropped by Der Regenbogenfisch, Public domain, via Wikimedia Commons
- Forktail blue-eye rainbowfish Dirk Godlinski, CC BY-SA 3.0, via Wikimedia Commons
- Red rainbowfish Hectonichus, CC BY-SA 3.0, via Wikimedia Commons
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