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Encyclopedia / Cichlids / Threadfin acara
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Variations

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Threadfin acara

Acarichthys heckelii · Acarichthys, Heckel's acara

Peaceful-to-semi-aggressive; keep with similar-sized fish.

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20 cmBody length, without tail ✓
24–28 °CTemperature ✓
6–8pH ✓
304 LSmallest tank ✓
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Tank mates
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Not recommended
  • Threadfin acara eats animals up to about 6 cm. Neon tetra only grows to 2.5 cm.
  • Only a narrow temperature range suits both: 24–25 °C.
Not recommended
  • Threadfin acara eats animals up to about 6 cm. Cardinal tetra only grows to 3 cm.
Not recommended
  • Threadfin acara eats animals up to about 6 cm. Black neon tetra only grows to 3.2 cm.
With conditions
  • Only a narrow temperature range suits both: exactly 24 °C.
With conditions
  • Only a narrow temperature range suits both: exactly 24 °C.
Compatible
Compatible
Compatible
Compatible
Compatible

291 species in our list are a good match.

Facts checked against sources on 16 Oct 2026. ✓ means a source backs it; ? means no reliable source yet. See sources

Care and water

Hardness ✓1–12 dGH
Group size ?Can live alone
Temperament ✓Semi-aggressive
Swims at ✓Middle
Care level ✓Moderate
Diet Omnivore
Lifespan ?Unknown
Size in shops 5–8 cm
Growth Medium

Behavior

Peaceful-to-semi-aggressive; keep with similar-sized fish. Will eat small tankmates.

  • sand

Food

Pellets, frozen foods and live worms.

Tap a food to see what it is.

Male or female

Hard to sex: mature females are noticeably thicker-bodied than males.

Health

Common problems. Tap one to see the signs. This is a guide, not a diagnosis.

Breeding

Open substrate spawner · Hard

Cave/burrow spawner: in the wild the female digs a burrow with a tunnel and egg chamber; she tends the eggs while the male guards the territory, and both guard the young. In aquaria an upturned flowerpot with a hole serves as the cave. Maturity takes 2-3 years.

Pairing

Grow out 6 juveniles and let a pair form; separate the pair if others are harassed.

Setup

A 250 L tank with a sponge or gentle filter, flat slate or rocks as spawning surfaces and a tight lid.

What starts it

Warm, clean water, frequent water changes and protein-rich food.

Eggs

200-400 eggs

Raising the fry

Parents move the wrigglers to pits and guard the free-swimming fry; feed newly hatched brine shrimp and crushed flake.

Common mistakes
  • Tank too small for a pair
  • Dirty water
  • Not removing the weaker partner when a pair fights
Full breeding guide, day-by-day plan and simulator →

Where it lives in the wild

RegionAmazon basin and Guianas
Rivers and lakesAmazon tributaries in Brazil, Peru and Colombia, and the Essequibo
HabitatRivers with sandy and muddy banks
Native rangeAbout 1,500 km across
See it on the world map

The story of the threadfin acara

The threadfin acara, only member of its genus, from the northern Amazon and the Essequibo in Guyana. It is named for the long free rays at the back of the dorsal fin and has a black streak below the eye, a black blotch on the front of the dorsal fin and a small black spot mid-flank.

Müller and Troschel described this cichlid in 1849, originally in Geophagus. It digs tunnels in the riverbank to spawn. Its long fin rays give it the name threadfin acara.

First described by Johannes Müller & Franz H. Troschel in 1849. Named for Named after Austrian ichthyologist Johann J. Heckel.

  • It digs tunnels in muddy banks to spawn.
  • Adults have long, flowing fin extensions.
  • It can reach around 20 cm.

Sources

14 facts checked with sources