Threadfin rainbowfish care guide

Plan a tank with threadfin rainbowfishSee all tank mates

Threadfin rainbowfish quick facts

• Known jumper: keep a tight-fitting lid.
• Long fins attract fin nippers.

Tank setup

A group of six needs at least 20 gallons (76 L) in a tank 24 in (60 cm) long, and a 30-gallon is better. Plant densely with fine-leaved stems and some floating plants, and keep the filter flow gentle. A lid helps, as small rainbowfish can jump.

How many threadfin rainbowfish in a tank?

The smallest common tank that suits threadfin rainbowfish is a 20 gallon. Here is roughly how many fit in each size when they are the only fish, based on adult size and waste output. Leave room if you want tank mates.

Water parameters

Keep it at 24–28 °C (75–82 °F), pH 6.0–7.5 and about 3–12 dGH. Unlike the big hard-water rainbowfish, it likes soft to moderately hard water. Keep the water clean and stable with small, regular water changes.

Best tank mates for threadfin rainbowfish

These popular species share threadfin rainbowfish' water needs and temperament. See the full list of 70 good matches.

• Cherry shrimp

  3 cm (1.2 in) · 20–27°C (68–81°F)

• Nerite snail

  2.5 cm (1 in) · 22–27°C (72–81°F)

• Guppy

  5 cm (2 in) · 22–27°C (72–81°F)

• Bristlenose pleco

  12 cm (4.7 in) · 22–26°C (72–79°F)

• Bronze corydoras

  7 cm (2.8 in) · 21–26°C (70–79°F)

• Assassin snail

  2.5 cm (1 in) · 22–27°C (72–81°F)

• Ramshorn snail

  2 cm (0.8 in) · 21–27°C (70–81°F)

• African dwarf frog

  3.5 cm (1.4 in) · 22–26°C (72–79°F)

Avoid keeping threadfin rainbowfish with

• Angelfish: Angelfish can eat threadfin rainbowfish: they're small enough to fit in its mouth once it's grown.
• Betta fish: Betta fish tends to attack colourful, long-finned fish like threadfin rainbowfish, mistaking them for rivals.
• Common goldfish: They need different temperatures: Threadfin rainbowfish 24–28°C (75–82°F), common goldfish 15–22°C (59–72°F).
• Fancy goldfish: They need different temperatures: Threadfin rainbowfish 24–28°C (75–82°F), fancy goldfish 18–23°C (64–73°F).
• Oscar: Oscar can eat threadfin rainbowfish: they're small enough to fit in its mouth once it's grown.
• Tiger barb: Tiger barb is a well-known fin nipper and will shred the long fins of threadfin rainbowfish.

Feeding

Its mouth is very small, so food must be tiny. Offer live or frozen baby brine shrimp, daphnia, cyclops and microworms, plus crushed flakes or micro pellets. Feed small amounts two or three times a day, and make sure faster fish do not eat everything first.

Behavior

It is very peaceful and easily outcompeted, so it does best alone or with other small, calm fish. Good mates include blue-eye rainbowfish (Pseudomugil), small rasboras, pygmy corydoras, otocinclus and dwarf shrimp. Never keep it with fin nippers such as tiger barbs or serpae tetras. Males spar over females, but injuries are rare.

Breeding

Males are larger and more colorful, with long, extended dorsal, anal and pelvic fins; females are plain with short fins. Use one male to two or three females. Females lay a few eggs a day on fine plants or a spawning mop, and adults eat eggs and fry, so move the eggs. They hatch in about 7–10 days, and the fry need infusoria or other very fine food.

Tips from experienced keepers

• Feed crushed flakes or micro pellets. Standard flakes are too big for their small mouths.
• Keep more females than males so the males can display without wearing each other out.
• Avoid any fish known to nip fins, even occasional nippers. The males' long fins are an easy target.
• Expect a short life of about 2–3 years. Breed a few if you want to keep them long term.
• Acclimate new fish slowly and start them on tiny live or frozen food.

Sources

We checked these references when writing this page. Values are for healthy long-term keeping, not survival limits. Last reviewed 2026-10-13. See our editorial policy.

• seriouslyfish.com
• fishbase.se
• en.wikipedia.org
• fishkeepingworld.com
• aquariumglaser.de