What size tank does a Threadfin Rainbowfish need?

Threadfin Rainbowfish needs a minimum of 15 gallons, with 20 gallons recommended. They are middle swimmers. Keep in groups of 6+.

Is Threadfin Rainbowfish good for beginners?

Threadfin Rainbowfish is rated "intermediate" difficulty (2/5). Great for beginners.

What fish are compatible with Threadfin Rainbowfish?

Threadfin Rainbowfish is peaceful. Compatible tank mates include other peaceful fish with similar water parameters (pH 5.5-7.5, temp 75-82°F).

Threadfin Rainbowfish

Iriatherina werneri

Family: Melanotaeniidae • Origin: Oceania

Male Threadfin Rainbowfish have spectacular elongated filaments on their fins. One of the most elegant small fish available.

Min Tank

15 gal

Max Size

Temperature

75-82°F

5.5-7.5

Lifespan

4 years

School Size

Swim Level

middle

Hardness

2-10 dGH

peacefulintermediateomnivoreschooling

Is Threadfin Rainbowfish Right for Your Tank?

Threadfin Rainbowfish is an excellent choice for beginners — rated "intermediate" difficulty (2/5). They're hardy, forgiving of minor water parameter fluctuations, and generally easy to feed. A 15-gallon tank minimum is standard — most community setups will accommodate them.

With a peaceful temperament, Threadfin Rainbowfish makes a great community fish. They coexist well with other non-aggressive species of similar size. This is a schooling species — keep at least 6 together, or they may become stressed and display abnormal behavior. Expected lifespan: 4 years with proper care.

Common Mistakes with Threadfin Rainbowfish

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Keeping fewer than 6 together

Threadfin Rainbowfish is a schooling species — they need a group of at least 6 to feel secure. Lone or paired individuals become stressed, hide constantly, and may develop health issues or aggression.

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Relying on a heater without a thermometer

Threadfin Rainbowfish needs 75–82°F. Heaters malfunction or drift over time — always use a separate thermometer to verify. Temperature swings of even 3–4°F can trigger stress and disease, particularly ich.

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Putting them in a tank under 15 gallons

Many beginners underestimate tank size needs. Threadfin Rainbowfish requires at least 15 gallons — ideally 20. Cramped tanks lead to stunted growth, aggression, and poor water quality.