Congo Tetra
Phenacogrammus interruptus
A stunning, medium-sized African characin famous for its shimmering iridescent scales and long flowy fins. Requires ample swimming space and soft water.
Water Temperature
24 - 28 °C
pH Value
6 - 7.5
Water type
Freshwater
Tank level
Middle
Adult size
10 cm
Minimum tank volume
>= 100 L
Minimum group
>= 6
GH
5 - 15 dGH
KH
2 - 7 dKH
TDS
95 - 295 ppm
Conductivity
148 - 461 uS/cm
Species description
Geographical Origin and Habitat: Native to the central Congo River basin in the Democratic Republic of the Congo (Central Africa). It inhabits rivers, streams, forest tributaries, and marshy lagoons. It prefers warm, soft, and slightly acidic waters shaded by the dense rainforest canopy, with sandy substrates covered by leaf litter, fallen branches, and submerged riparian vegetation.
Taxonomy and Morphology: Belongs to the family Alestidae, genus Phenacogrammus. Described by Boulenger in 1899. It features a tall, laterally compressed, oval-shaped body. Mature males develop highly elongated dorsal and caudal fins, with a characteristic central filament extending from the caudal fin. Males reach a maximum length of 8.0-10.0 cm (3-4 inches), while females remain smaller at 6.0-7.0 cm.
Social Behavior: A peaceful, active, and strictly schooling fish. It must be kept in schools of at least 6-8 individuals; if kept singly or in too small a group, it becomes extremely shy, stressed, and will lose its brilliant coloration. It swims primarily in the middle layers of the aquarium, moving gracefully in a group.
Coloration and Sexual Dimorphism: The coloration is spectacular and highly iridescent, featuring a golden-yellow horizontal band along the flanks, highlighted by shifting reflections of blue, green, and red depending on the light angle. Sexual dimorphism is pronounced: males are larger, display beautifully trailing and fringed fins, and show far more vibrant colors than the smaller, short-finned females.
Care, breeding and tankmates
Aquarium Setup: Requires a spacious aquarium with a minimum length of 100-120 cm (at least 150-200 liters / 40-50 gallons for a school). The setup should provide plenty of open swimming space in the center, with dense planting along the sides and back (such as Anubias, Bolbitis, and Vallisneria). Dark sandy substrate and driftwood roots help diffuse light and reduce stress.
Diet and Feeding: An omnivore that feeds on insects, small crustaceans, and plant matter in the wild. In the aquarium, it readily accepts high-quality flakes and pellets. It is essential to regularly supplement their diet with live or frozen foods (brine shrimp, bloodworms, mysis, fruit flies) and vegetable-based foods containing spirulina to support health and color.
Water Quality: Demands high and stable water quality. Optimal parameters are a temperature of 23-27°C (73.4°F - 80.6°F), a slightly acidic to neutral pH (6.0 - 7.5), and soft to medium water hardness (GH 4-12 dGH). Sensitive to nitrate and phosphate accumulation; requires efficient filtration with moderate water flow, and regular partial water changes.
Compatibility and Cohabitation: Excellent fit for medium-sized community aquariums. It coexists peacefully with other quiet fish such as cyprinids, other tetras, dwarf cichlids (e.g., Pelvicachromis), benthic catfish (Corydoras, Loricariids), and small gouramis. Avoid keeping with aggressive, territorial, or fin-nipping fish (such as some barbs) that could damage the males' long fins.
Aquarium Breeding: Moderately difficult to breed. Requires a dedicated breeding tank filled with very soft (GH < 4) and acidic (pH 6.0) water, with Java moss or a spawning grid at the bottom to protect the eggs. Spawning occurs after active courtship. Remove parents immediately after spawning. Eggs hatch in about 6 days; feed fry with infusoria and brine shrimp nauplii.
Risks and Diseases: Susceptible to bacterial fin rot and Ich if stressed by poor water quality or aggressive tankmates. Maintaining stable parameters and regular water changes prevents most diseases. Acclimate new specimens slowly to prevent pH shock.
Geographic Origin and Distribution
Native to the central Congo River basin in the Democratic Republic of the Congo (Central Africa). It inhabits rivers, streams, forest tributaries, and marshy lagoons. It prefers warm, soft, and slightly acidic waters shaded by the dense rainforest canopy, with sandy substrates covered by leaf litter, fallen branches, and submerged riparian vegetation.
Origin
Tropical oceans and reefsAfrica and Madagascar
Fish profile
- Temperament
- Semi-aggressive
- They possess a generally peaceful but somewhat skittish temperament, especially if kept in groups that are too small. When kept in a proper school of six or more, they feel secure and become bold, active participants in the community tank. They can be easily intimidated by large, boisterous, or aggressive fish, which may cause them to hide and lose their coloration. Providing a calm environment with appropriate tank mates allows their peaceful and elegant nature to shine.
- Diet
- Omnivore
- Congo tetras are omnivorous and require a diverse diet to support their growth and maintain their stunning iridescent colors. They readily consume high-quality flake and pellet foods designed for community fish. Supplementing their diet with live or frozen foods like bloodworms, daphnia, and brine shrimp is crucial for conditioning and overall vitality. Incorporating some plant-based matter or vegetable flakes will also help replicate their varied natural diet.
- Life expectancy
- 4-8 years
- The Congo tetra has a lifespan of 4 to 8 years when cared for under optimal conditions. To achieve this life expectancy, it is essential to maintain excellent water quality with a very low concentration of organic waste. A varied diet and minimizing stress from inappropriate tank mates significantly contribute to their long-term health.
- Adult size
- 10 cm
- The catalog's scalar value is 10 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 8 cm for this species, recorded as total length (TL). The taxonomic record consulted is Phenacogrammus interruptus (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- School
- It is highly recommended to keep them in a mixed-sex school with a roughly equal ratio of males to females, or slightly more females. The males, which are larger and more brightly colored with extended finnage, will display constantly to attract females. Having multiple females helps disperse any chasing behavior and reduces stress on individual fish. A proper sex ratio ensures the display of their most vibrant colors and natural schooling dynamics.
- Feeding frequency
- Twice daily
- These active swimmers should be fed one to two times daily with amounts they can entirely consume within a few minutes. Their energetic nature means they have a healthy appetite, but overfeeding can quickly degrade water quality. It is important to distribute the food evenly across the water surface to ensure all individuals in the school get their fair share. Fasting them for one day a week can promote good digestion and prevent bloating issues.
- Bioload
- Congo tetras have a moderate bioload due to their active nature and schooling behavior. As they are best kept in groups of at least six individuals, their collective waste production can be significant. A robust filtration system and regular partial water changes are essential to keep nitrate levels low and maintain pristine water quality. Their active metabolism demands efficient biological and mechanical filtration to ensure a healthy environment.
- Flow
- Stagnant
- Originating from the Congo River basin, they appreciate moderate to moderately strong water flow in the aquarium. The current should provide enough movement to stimulate their natural schooling behavior and keep the water highly oxygenated. While they enjoy swimming against a steady flow, they also require densely planted areas where the water is calmer for resting. A balanced flow dynamic is key to keeping these fish healthy and displaying their best behaviors.
- Reproduction
- Oviparous
- Breeding Congo tetras is possible but challenging, requiring a dedicated breeding tank with soft, acidic water and subdued lighting. They are egg scatterers and do not exhibit any parental care, often eating their own eggs if given the chance. A layer of marbles or a breeding mesh at the bottom of the tank is necessary to protect the eggs from the adults. The fry are quite small and require infusoria or finely powdered foods immediately after absorbing their yolk sacs.
- Compatibility & tankmates
- This species is highly peaceful and makes an excellent addition to large community freshwater aquariums. They are best kept with other similarly sized, peaceful fish such as larger rasboras, peaceful cichlids, and bottom-dwelling catfish. Fin-nipping species should be strictly avoided, as the trailing fins of the male Congo tetras are easily damaged. They thrive in a calm environment where they are not bullied or outcompeted for food by overly aggressive tank mates.
- Tank level
- Middle
- Congo tetras are classic mid-water swimmers, occupying the middle to upper levels of the aquarium water column. They are incredibly active and require a long tank with plenty of open swimming space to accommodate their energetic schooling. While they appreciate the cover of tall plants along the back and sides, they avoid dense vegetation that restricts their movement. Their constant activity adds dynamic movement and a brilliant flash of color to the center of the aquarium display.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3 ± 0.33 se
- Resilience
- High (less than 15 months)
- Phylogenetic uniqueness (PD50)
- 0.502
- Bayesian Length-Weight
- a = 0.01072, b = 3.02
- VulnerabilityLow vulnerability (10 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
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