Threadfin Rainbowfish (Iriatherina werneri) is an intermediate-level freshwater fish that needs at least 20 gallons and 74-82°F. A tiny rainbowfish whose males have long trailing fins. It is more delicate than other rainbowfish, so use calm tankmates and avoid fin nippers, strong flow and sudden water changes.
Care facts at a glance
| Scientific name | Iriatherina werneri |
|---|---|
| Family | Melanotaeniidae |
| Origin | New Guinea and northern Australia |
| Adult size | 2 in |
| Minimum tank | 20 gallons |
| Temperature | 74-82°F |
| pH | 6.0-7.5 |
| Temperament | Peaceful, delicate |
| Social behavior | Groups of 6+ |
| Swim level | Upper to mid |
| Difficulty | Intermediate |
| Diet | Micro pellets, baby brine shrimp, small frozen foods |
| Typical lifespan | 2-3 years |
Quick tips
- Keep a group with extra females.
- Provide gentle flow and plants.
- Not a good match for fin nippers.
San Diego water
Captive-bred stock usually adapts to San Diego tap water with slow acclimation. For best color and health, many keepers blend tap with RO/DI water. Learn the numbers in our San Diego tap water guide.
Before you buy
Make sure your tank is cycled (how to cycle a tank), check your numbers with the water testing guide, and use the compatibility guide to check tankmates. These are general ranges; individual fish and local water vary.
Find it at Pet Zone
Pet Zone Tropical Fish is a San Diego aquarium store with two locations. Stock changes daily, so call ahead if you are after a specific species or plant. Shop online at petzonesd.com.
4160 Convoy St, San Diego, CA 92111
(858) 987-0309
Open daily, 10am-6pm
Aquascaping, planted tanks
4266 University Ave, San Diego, CA 92105
(619) 283-1812
Closed Monday; Tue-Fri 10:30am-6pm, Sat 11am-6pm, Sun 11am-4pm
Monster fish, koi