Congo tetra

Quick facts

Adult size

8.5 cm

Lifespan

can live up to 5 years; 3-5 years typical

Tank zone

mid

Temperament

peaceful

Difficulty

intermediate

Schooling

recommended 6+ (critical minimum 5, thrives at 8+)

Water parameters

Temperature

23–28°C

pH

6.0 to 7.5

Hardness

1 to 12 dGH

Tank requirements

Minimum volume

200 L

Minimum length

120 cm

Flow

low

Lighting

dim preferred

Substrate

any

Driftwood

preferred

Open swimming room

needed

Lid

required - jumper

Feeding

Diet: omnivore, feeds primarily at the mid.

Omnivore with a larger appetite than most tetras. Standard flake food, pellets, frozen bloodworm, frozen brine shrimp, frozen daphnia, and live food. Will also eat vegetable matter: blanched peas, spirulina flake, and algae. Feed twice daily. The large body means they need more food than a neon or ember tetra school of equal numbers. Frozen food and live food maintain the iridescent sheen on the scales.

Vegetable matter required (algae wafers, blanched zucchini, spinach).

Compatibility

• Peaceful, large-bodied tetra (8–10 cm adult) that needs a bigger tank than most tetra keepers expect. A school of 8 congo tetras needs at least a 200-liter tank because of their active swimming and adult body size.
• Males develop long, flowing fin extensions that make them beautiful but also a target for fin-nippers. Avoid housing with tiger barbs, serpae tetras, and any known nipper.
• Good with medium-sized community fish: rainbow fish, larger barbs (rosy, denison), larger catfish, and other peaceful cichlids. Too large to be eaten by most community predators.
• Schooling species that looks best in groups of 8+. Males display their iridescent colors and flowing fins more intensely when competing for female attention. A group of 6+ males with a similar number of females is spectacular.

Habitat

Native to the Congo River basin in the Democratic Republic of the Congo, Republic of the Congo, and Central African Republic. Found in large, slow-moving sections of the Congo and its tributaries, in turbid water over sandy substrates. The species is one of the showpiece tetras of the African continent. Males develop extraordinary iridescent coloring at maturity: the body shimmers with blue, green, gold, and orange depending on the light angle. The dorsal, anal, and caudal fins extend into long, flowing filaments in mature males. Females are plainer but still attractive, with a golden-olive body and shorter fins. Adult males reach 8–10 cm; females are slightly smaller. Described by Boulenger in 1899, the species entered the hobby trade in the 1960s. All hobby stock is tank-bred, primarily in Southeast Asian and Eastern European farms. Wild-caught specimens occasionally appear in specialist imports.

Breeding

Egg scatterer, moderate difficulty. Requires soft, acidic water (pH 6.0-6.5, GH below 5) and a large breeding tank (100 L) because the spawning chase covers a lot of ground. Condition a group with live and frozen food for 2 weeks. Spawning occurs at dawn. Eggs are scattered among fine-leaved plants and are light-sensitive. Remove adults after spawning. Eggs hatch in 5-7 days (slower than most tetras). Fry are relatively large and can eat baby brine shrimp shortly after becoming free-swimming. Growth is slow for the first month, then accelerates. Males begin developing their fin extensions at around 3-4 months. The species is bred commercially but is less prolific than small tetras, which contributes to its higher price in stores.

Common problems

Fin damage from nipping tankmates or from rough handling during netting. The long, filamentous fins of males are delicate and tear easily. Damaged fins regrow but the process takes weeks. Ich in newly purchased fish is the standard disease risk. Congo tetras are sensitive to poor water quality; they show stress (clamped fins, faded color, loss of iridescence) before many other species react. This makes them a useful indicator fish: if the congos look bad, something is wrong with the water. Columnaris infections appear in dirty tanks. The species is moderately sensitive to medication; use reduced doses of copper-based treatments. The main non-medical issue is inadequate tank size: people buy 6 juveniles for a 75-liter tank and discover that adult congos at 8–10 cm with flowing fins need substantially more space.

Bioload

Bioload coefficient: 2.6 (active swimmer, larger than typical tetras; per-cm load similar to a small barb).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size