Congo Tetra 3–4cm (Phenacogrammus interruptus) – Live Aquarium Fish

Congo Tetra 3–4cm (Phenacogrammus interruptus) is a beautiful African schooling fish known for its shimmering rainbow colours and graceful swimming behaviour. As these peaceful tetras mature, their bodies develop iridescent blue, violet, green and golden tones that make them a standout addition to a planted freshwater aquarium.

Male Congo Tetras are especially impressive, developing elegant extended dorsal and tail fins as they mature. Their active schooling behaviour and attractive colouration make them a popular choice for larger tropical community aquariums.

Our Congo Tetras are supplied at approximately 3–4cm. These are young fish that may not yet display their full adult colours or fin development.

Why Choose Congo Tetras?

• Beautiful rainbow colours: Mature fish display shimmering blue, violet, green and golden tones.
• Elegant flowing fins: Adult males develop distinctive extended dorsal and tail fins.
• Peaceful temperament: Suitable for larger tropical community aquariums with compatible fish.
• Active schooling behaviour: Particularly impressive in groups of eight or more.
• Excellent for planted tanks: Their colours stand out against green aquarium plants and darker substrates.
• Easy to feed: Accepts quality tropical fish foods and appropriately sized frozen or live foods.

Congo Tetra Fish Profile

• Scientific name: Phenacogrammus interruptus
• Common name: Congo Tetra
• Family: Alestidae
• Origin: Congo River basin, Central Africa
• Sale size: Approximately 3–4cm
• Adult size: Males approximately 8cm; females approximately 6cm, with some variation
• Temperament: Peaceful, active and social
• Care level: Easy to moderate
• Recommended group: 8–10 or more
• Recommended adult aquarium: Approximately 150–200 litres or larger, with a minimum 120cm swimming length preferred
• Temperature: 23–28°C
• pH: 6.0–7.5
• General hardness: 3–18 dGH
• Diet: Omnivore
• Swimming level: Mainly middle water levels
• Suitable aquarium: Larger planted tropical community aquarium

Beautiful Colours That Develop With Age

Young Congo Tetras can appear relatively plain compared with their spectacular adult appearance.

As they mature, their scales develop an iridescent finish that reflects different colours depending on the aquarium lighting and viewing angle.

Adult males generally display stronger colours and longer, more elaborate fins. Females are typically smaller, with shorter fins and more subdued colouration.

Please note: Fish supplied at 3–4cm are juveniles. Colour, fin development and sex may vary, and mature male colouration cannot be guaranteed.

How Many Congo Tetras Should You Keep?

Congo Tetras are naturally social fish and should be maintained in groups rather than individually.

We recommend keeping at least eight to ten Congo Tetras together in a suitably sized aquarium.

A larger group helps the fish feel more secure and encourages natural schooling and social behaviour. Keeping too few can result in shy or easily startled fish.

Allow plenty of open swimming space so the group can move comfortably through the middle of the aquarium.

Ideal Aquarium Setup

Congo Tetras are best suited to spacious, established aquariums with plants around the edges and clear swimming space through the centre.

For an attractive setup, provide:

• Open swimming space: A tank at least 120cm long is preferred for an adult group.
• Aquarium plants: Use taller plants along the rear and sides to create cover.
• Floating plants: Help create shaded areas and a more secure environment.
• Driftwood: Adds natural structure and shelter.
• Darker substrate: Can help highlight the fish's shimmering colours.
• Suitable filtration: Maintain clean, well-oxygenated water with gentle to moderate circulation.
• Secure lid: Congo Tetras can jump when startled.

Browse our aquascaping supplies for materials to create a natural planted aquarium.

Congo Tetra Water Parameters

Congo Tetras prefer clean, stable freshwater and generally do best in slightly acidic to neutral conditions.

• Temperature: 23–28°C
• pH: 6.0–7.5
• General hardness: 3–18 dGH
• Ammonia: 0ppm
• Nitrite: 0ppm
• Nitrate: Keep low through regular maintenance and water changes

Stable water conditions are particularly important. Poor water quality can affect their colour, health and fin development.

Only introduce Congo Tetras into a fully cycled aquarium with suitable water parameters.

Suitable Congo Tetra Tank Mates

Congo Tetras are generally peaceful and can be housed with other non-aggressive tropical fish that enjoy similar water conditions.

Suitable companions may include:

• Peaceful Rainbowfish: Species with compatible adult size and water requirements.
• Corydoras Catfish: Peaceful bottom dwellers suited to the same conditions.
• Selected Peaceful Tetras: Fish large enough to coexist comfortably with active adult Congo Tetras.
• Peaceful Gouramis: Carefully selected species that are not overly timid.
• Selected Peaceful Dwarf Cichlids: Where tank size, temperament and water conditions are suitable.

Avoid aggressive fish and known fin-nipping species such as Tiger Barbs and Serpae Tetras, which may damage the extended fins of mature males.

Very timid fish may also be unsettled by an active group of adult Congo Tetras.

What Do Congo Tetras Eat?

Congo Tetras are omnivores that naturally consume small insects, worms, crustaceans and other available foods.

In the aquarium, provide a varied diet including:

• High-quality tropical fish flakes.
• Appropriately sized tropical micro pellets.
• Frozen or live brine shrimp.
• Frozen Daphnia.
• Appropriately sized bloodworms and other suitable invertebrate foods.

Offer small portions once or twice daily. A varied diet containing suitable live or frozen foods can support healthy colouration and body condition.

Explore our aquarium fish food range for suitable tropical fish foods.

Are Congo Tetras Suitable for Beginners?

Congo Tetras can be an excellent choice for fishkeepers with a properly established aquarium and enough room for a group.

They are generally peaceful and readily accept prepared foods, but their adult size, active swimming behaviour and sensitivity to poor water quality make them less suitable for small or newly established aquariums.

With adequate space, clean water and compatible tank mates, they can become a spectacular centrepiece schooling fish.

Frequently Asked Questions

How big do Congo Tetras grow?

Adult males generally reach approximately 8cm, while females are usually smaller at around 6cm. Fish supplied at 3–4cm are juveniles.

What pH do Congo Tetras prefer?

Congo Tetras are generally suited to a pH of approximately 6.0–7.5. Stable, clean freshwater is important for their long-term health.

How many Congo Tetras should I keep?

We recommend a group of at least eight to ten individuals in a suitably sized aquarium. Larger groups encourage natural schooling behaviour.

Do Congo Tetras develop more colour as they grow?

Yes. Juveniles often appear relatively plain, while mature fish develop beautiful iridescent colours. Males generally develop the strongest colouration and longest fins.

Are Congo Tetras aggressive?

No. Congo Tetras are generally peaceful, although they are active swimmers and may unsettle very shy or delicate tank mates.

What size aquarium do Congo Tetras need?

A mature group is best housed in an aquarium of approximately 150–200 litres or larger, preferably at least 120cm long to provide ample swimming space.

Can Congo Tetras live in planted aquariums?

Yes. They look particularly attractive in planted aquariums with tall plants around the edges and open swimming space through the centre.

What do Congo Tetras eat?

They accept quality tropical flakes and small pellets, along with appropriately sized live or frozen foods such as Daphnia and brine shrimp.

Are the Congo Tetras sold at 3–4cm fully coloured males?

No. These are juvenile fish, and their final colouration, fin development and sex cannot be guaranteed.