Congo Tetra
Phenacogrammus interruptus
A hardy, active South American tetra known for its silvery body, dark-edged fins and energetic schooling behaviour.
Difficulty
Beginner
Min tank size
110 L / 29 gal
Temperament
Peaceful, active
Diet type
Omnivore
Adult size
7–8 cm / 2.8–3.1 in
Lifespan
5–8 years
Water type
Freshwater
Congo tetra at a glance
| Scientific name | Phenacogrammus interruptus |
|---|---|
| Order | Characiformes |
| Family | Alestidae |
| Genus | Phenacogrammus |
| Origin | South America — Democratic Republic of the Congo — Congo River basin in Central Africa |
| Adult size | About 7–8 cm (2.8–3.1 in) |
| Tank size (min) | 110 L / 29 gal for a school; a longer footprint is preferred |
| Temperature | 23–28 °C (73–82 °F) |
| pH range | 6.0–7.5 |
| Water hardness | Soft to moderately soft |
| Diet | Omnivore — flakes, pellets, frozen and live foods |
| Temperament | Peaceful, energetic schooling fish |
| Care level | Beginner |
Overview
The Congo tetra (Phenacogrammus interruptus) is a robust South American characin that has been popular in the aquarium hobby for decades. Its silvery body, darker dorsal and anal fins and warm red accents make it easy to recognise, while its energetic nature gives a community aquarium plenty of movement.
This is a more substantial tetra than many nano species. It is peaceful enough for a community aquarium, but its constant swimming and occasional fin-nipping mean it should be kept with appropriately sized, active tankmates. A proper school and a long aquarium are much more important than keeping it in a small decorative tank.
Congo tetra size & lifespan
How big do Congo tetras get?
Adults usually reach about 4–5 cm (1.6–2 inches). Females can look deeper-bodied than males, especially when mature and carrying eggs.
How long do Congo tetras live?
In a clean, stable aquarium, Congo tetras can live around 5–8 years, sometimes longer. A varied omnivore diet, good filtration, regular maintenance and sufficient swimming space are key factors in keeping them healthy over the long term.
Natural habitat & origin
Phenacogrammus interruptus is native to the upper Amazon and Orinoco drainage systems of northern South America, especially the Rio Negro region of Brazil and parts of Colombia. Wild fish are associated with slow-moving, shaded blackwater environments where leaf litter, submerged roots and dense vegetation provide cover and feeding opportunities.
Most aquarium specimens are captive-bred and should be acclimated carefully to stable, clean water. A planted aquarium with open swimming space, moderate current, good oxygenation and stable water conditions provides a suitable captive environment without needing to duplicate every detail of the wild habitat.
Congo tetra tank size & requirements
A 29-gallon (110 L) long aquarium is a sensible minimum for a school of Congo tetras. The species is active and can reach a substantial size for a tetra, so horizontal swimming room is more useful than extra tank height. A secure lid is recommended because active tetras can jump when startled.
How many Congo tetras in a 10 or 20 gallon tank?
A 10-gallon aquarium is generally too cramped for a proper long-term school. In a 29-gallon tank, a group of six to eight is a reasonable starting point when filtration and maintenance are strong. Larger aquariums are better for larger groups and mixed community stocking.
| 5 gal (19 L) | Not recommended — too small for an active school of Congo tetras. |
|---|---|
| 10 gal (38 L) | Not recommended as a long-term home; a school needs more swimming room and stable water quality than a small nano aquarium can reliably provide. |
| 29 gal (110 L) | A practical minimum for a school of 6–8, preferably in a longer aquarium. |
| 29 gal (110 L) | 8–12 Congo tetras, with room for compatible peaceful tankmates. |
| 55 gal (208 L) | A larger school of 10–18 can work well, with substantial swimming space and careful community stocking. |
Water parameters
| Temperature | 23–28 °C (73–82 °F) |
|---|---|
| pH | 6.0–7.5 |
| Hardness (GH) | Soft to moderately soft |
| Filtration turnover | Moderate circulation with good oxygenation |
Use a fine sand or smooth gravel, hardy live plants and an unobstructed swimming lane through the middle of the aquarium. Congo tetras may nibble tender vegetation, so tougher plants are a safer choice than delicate soft-leaved species. Moderate filtration and good oxygenation suit their active nature.
Not sure how many litres your tank holds? Check it with theaquarium volume calculator.
What do Congo tetras eat? Diet & feeding
Congo tetras are unfussy omnivores. A quality flake or appropriately sized pellet makes a good daily staple, while frozen or live foods such as daphnia, brine shrimp and bloodworms provide variety and useful enrichment.
Feed small portions once or twice daily and provide only enough food for the school to finish in a few minutes. Because these fish are active feeders, overfeeding is easy and can quickly contribute to poor water quality.
Congo tetra tank mates & compatibility
Keep Congo tetras in a school of at least six. They are peaceful by nature, but their energetic swimming style makes them a better match for robust, similarly active community fish than for timid nano species.
Are Congo tetras aggressive? They are not usually aggressive, but individuals may chase one another or nip fins. This behaviour becomes more noticeable in cramped tanks or when they are kept in an undersized group. Spacious aquariums and compatible tankmates are the best prevention.
Good Congo tetra tank mates
- Other peaceful, similarly sized tetras and characins
- Larger peaceful rasboras and active community schooling fish
- Corydoras catfish suited to the same temperature range
- Peaceful loaches and other bottom-dwelling community fish
- Bristlenose plecos in appropriately sized mature aquariums
- Peaceful medium-sized livebearers when water chemistry overlaps
- Other robust community fish that can tolerate their active swimming
Avoid
- Large predatory fish that can swallow adult Congo tetras
- Highly aggressive or territorial cichlids
- Very slow, delicate or long-finned fish that may be stressed by their activity
- Tiny shrimp and newly hatched fry, which may be eaten
How to breed Congo tetras
Congo tetras are egg-scattering fish that can spawn when mature adults are well conditioned when adults are healthy and well conditioned. Feed a varied, nutritious diet for several days before moving selected adults to a separate breeding aquarium.
Use fine-leaved plants, a spawning mop or a protected spawning grid to catch the eggs, provide gentle aeration and keep lighting subdued. Remove the adults after spawning because they may eat the eggs. Once the fry hatch, provide suitably tiny first foods and gradually transition them to newly hatched brine shrimp and other larger foods as they grow.
Naming & buyer’s notes
Congo tetra is the standard aquarium name for Phenacogrammus interruptus, a larger African characin prized for its iridescent colours and flowing fins. When buying, choose active fish with clear eyes, intact fins, good body condition and strong interest in food. Avoid specimens that remain lethargic, have clamped fins or show obvious signs of disease.
A larger tetra
Do not plan for this species like a tiny nano tetra. Its adult size and constant activity make a longer aquarium much more appropriate.
Plant selection
They are generally plant-safe. Dense planting and floating cover can provide useful shade and help the school feel secure.
Buy a group
A school is essential for normal social behaviour. Buying several healthy specimens together is preferable to keeping a single Congo tetra as a display fish.
Congo tetra FAQ
- How big do Congo tetras get?
- Congo tetras commonly reach around 7–8 cm (2.8–3.1 inches) in aquariums, with males often developing longer, more flowing fins than females.
- How long do Congo tetras live?
- With stable water quality, a varied diet and appropriate tank conditions, Congo tetras can commonly live around 5–8 years in captivity.
- How many Congo tetras should be kept together?
- Keep Congo tetras in a group of at least six. Larger groups generally display more natural schooling and social behaviour when the aquarium provides enough swimming room.
- What size tank do Congo tetras need?
- A 29-gallon (110 L) long aquarium is a sensible minimum for a proper group. Larger tanks are preferable because these fish are active swimmers and males develop flowing fins.
- What do Congo tetras eat?
- They are omnivores and accept quality flakes, pellets, frozen foods and live foods such as daphnia, brine shrimp and bloodworms. Variety helps maintain colour and condition.
- Are Congo tetras aggressive?
- Congo tetras are generally peaceful. Males may display to each other, but serious aggression is uncommon. Avoid aggressive fish and fin-nippers that may damage their long fins.
- Can Congo tetras live with other community fish?
- Yes. They work well with peaceful, similarly sized community fish that appreciate compatible water conditions. Avoid large predators, aggressive cichlids and persistent fin-nippers.
- How do you breed Congo tetras?
- Congo tetras are egg-scatterers. Condition adults with varied foods, move them to a separate breeding aquarium with subdued lighting and spawning media, and remove the adults after spawning because eggs may be eaten.