Congo Tetra Care Guide: Tank Size, Diet & Tank Mates (Phenacogrammus interruptus)

The Congo Tetra (Phenacogrammus interruptus) is one of the most stunning freshwater schooling fish you can keep — iridescent blue, gold, and violet scales, flowing veil-like fins on adult males, and a peaceful temperament that fits beautifully in a planted community aquarium. They're not a beginner fish exactly, but they're not difficult either. The trick is giving them the three things they really need: a long tank, soft and slightly acidic water, and a proper school. Get those right and you'll watch one of the most underrated showpieces in the hobby light up your tank for 5+ years.

This guide covers everything: tank size and aquascape, water parameters, diet (they're surprisingly picky for tetras), schooling group size, the best and worst tank mates, sexing males from females, breeding tips, and a full FAQ.

Congo Tetra Quick Care Sheet

• Scientific name: Phenacogrammus interruptus
• Adult size: Males 3.0–3.5 in, females 2.5 in
• Minimum tank size: 30 gallons (40+ strongly preferred for a proper school)
• Schooling group: Minimum 6, ideally 8–10
• Temperature: 73–82°F
• pH: 6.0–7.5 (soft, slightly acidic is best)
• Hardness: 4–18 dGH (prefer the softer end)
• Lifespan: 4–6 years
• Temperament: Peaceful, but skittish in small groups
• Difficulty: Easy–Intermediate

Natural Habitat & Background

Congo Tetras come from the slow-moving tributaries and streams of the Congo River Basin in Central Africa. The water there is soft, slightly acidic, tannin-stained from leaf litter, and shaded by overhanging vegetation. Replicating those conditions at home — dim light, dark substrate, plants, and driftwood — does two things at once: it lowers their stress and makes their iridescence absolutely pop. Bright bare tanks wash them out and make them spooky; planted blackwater-ish setups bring them to life.

Appearance & Sexing Males vs Females

Adult male Congos are the showpieces. They develop long flowing extensions on the dorsal, anal, and tail fins, often described as "veil tails." Their bodies shimmer with blue, gold, green, and violet depending on the angle, and they're noticeably larger than females. Females stay smaller, rounder when full of eggs, with shorter fins and a more subdued silvery coloration.

When you're buying Congo Tetras, juveniles look nearly identical — drab silver with a faint stripe. The color and fin extensions develop over 9–12 months as they mature. Don't judge an adult Congo by a juvenile photo.

Tank Size & Aquascape

Congo Tetras are active mid-water schoolers and they swim a lot. They need horizontal space more than depth. We recommend a 40-gallon long or larger as the practical minimum for a school of 8. You can keep 6 in a standard 30, but they'll feel cramped and their behavior won't be as natural. In a 55–75 gallon you'll see them at their best.

[IMAGE 2 HERE — planted tank with dark substrate]

Substrate

Dark substrate dramatically improves their coloration — think black sand or a dark planted-tank substrate. White or bright gravel will make them appear pale and stressed.

Plants & Driftwood

Plants and wood are not optional. Congos are an open-water school but they want plant cover at the edges and shaded areas to retreat into. Hardy, low-light plants work perfectly. Good choices from our stock:

• Anubias barteri — attach to driftwood, indestructible
• Java Fern — same idea, attach to wood or rock
• Jungle Vallisneria — tall background plant for shade
• Corkscrew Vallisneria — adds movement
• Cryptocoryne wendtii 'Brown' — bronze midground

For driftwood, our Malaysian Driftwood sinks immediately and slowly releases tannins, which is exactly what Congos like. If you want a full blackwater look, add a couple of Indian almond leaves to the tank — your Congos' colors will deepen within days. Browse the full live aquatic plants collection or start with the Beginner Plant Pack if you're new to live plants.

Lighting

Congos prefer dim to moderate light. Bright high-output lighting stresses them. A Hygger 20W full-spectrum LED on a low setting or shaded with floating plants is ideal. Adding floaters like Red Root Floaters or Frogbit (see our floating plants collection) breaks up overhead light and brings out their iridescence.

Filtration & Flow

Aim for 5–6x turnover with a quality canister or HOB filter from our filtration collection. Congos like a gentle current — they evolved in slow-moving water, so avoid powerheads pointed across the tank. They appreciate well-oxygenated water but not whitewater.

Water Parameters

Aim for the soft, slightly acidic end of the tropical range:

• Temperature: 75–80°F (use a reliable heater)
• pH: 6.0–7.0 ideal (they tolerate up to 7.5)
• GH: 4–10 dGH
• Ammonia/nitrite: 0 ppm — non-negotiable
• Nitrate: below 20 ppm

Make sure your tank is fully cycled before adding Congos — they don't tolerate ammonia spikes. If you're new to cycling, read our fishless vs fish-in cycling guide first. Dose Seachem Prime or a quality water conditioner at every water change.

Diet & Feeding

Congo Tetras are omnivores with a surprise twist: they're flake-shy nibblers. They often refuse food that drops too fast or sits at the bottom, and they're easily out-competed at feeding time by faster mid-water fish. Variety and slower-sinking foods are the answer.

Daily Staple

• Xtreme Community Crave Flakes — high-protein, sinks slowly
• Xtreme Community Flakes — daily tropical staple
• Small slow-sinking micro pellets from our pellets collection

Weekly Treats (critical for color and breeding)

• Frozen bloodworms, brine shrimp, and mysis from our frozen food collection
• Live blackworms when available
• Daphnia for digestion and color

Feed small amounts 2x daily rather than one big meal — Congos graze. If you have shy individuals, dim the lights and feed; they're much braver in low light.

Schooling Behavior & Group Size

This is the single most-broken rule when people keep Congos. They are not "loose schoolers" — they are an obligate schooling species and they suffer when kept in small groups. A school of three or four Congos will hide constantly, lose color, refuse food, and develop chronic stress.

Minimum is six. The right answer is eight to ten or more. A school of 10 in a 55-gallon planted tank is one of the most beautiful sights in freshwater fishkeeping. They'll shoal together by day and spread into a loose group at feeding time.

Best Tank Mates for Congo Tetras

Congos are peaceful and pair well with other peaceful soft-water species. Pick tank mates that share their water preferences and don't out-compete them at feeding time. Being large for a tetra, they are also one of the safer schooling fish to keep with angelfish — see our guide to the best tank mates for angelfish. Their tolerance for warm, soft water also makes them a solid choice for the best tank mates for discus.

Great Choices

• Corydoras catfish — peaceful bottom dwellers; see our Corydoras care guide
• Rummynose Tetras — tight schoolers that pair beautifully
• Other peaceful tetras like Black Phantom or Diamond
• Bristlenose Plecos — see our full pleco care guide
• Peaceful dwarf cichlids like German Blue Rams or Apistogramma
• Honey Gouramis or other peaceful gouramis
• Otocinclus for algae cleanup

Avoid

• Aggressive cichlids (most Africans, large South Americans)
• Fin nippers — Tiger Barbs, Serpae Tetras in small groups, Black Skirt Tetras in small groups
• Fast aggressive feeders that bully them away from food
• Very small nano fish (under 1") — Congos may snap at them
• Shrimp — adult Congos will hunt cherry shrimp; Amano shrimp are usually safe but not guaranteed

Breeding Congo Tetras

Breeding Congos is achievable but requires a dedicated setup. They're egg scatterers that drop eggs over fine-leaved plants or a spawning mop, and the parents will eat the eggs if left in. Most hobbyists struggle because they try to breed in the display tank — set up a separate breeder.

Breeder Setup

• 10–20 gallon bare-bottom tank
• Soft, acidic water: pH 5.5–6.5, GH under 4
• Peat-filtered or RO/tap mix to achieve those parameters
• Temperature around 78°F
• Dim light — heavy floating plants or paper over the tank
• Spawning mop or thick clump of Java moss

Conditioning & Spawning

Condition a known male/female pair (or two males and three females) for 1–2 weeks on heavy live and frozen food in the main tank. Move them to the breeder in the evening. Spawning usually happens at dawn — eggs drop and roll into the mop. Remove the adults immediately after, dim the tank, and treat with a mild fungicide. Fry hatch in 6–7 days and become free-swimming a few days later. Feed infusoria, then baby brine shrimp.

Common Health Issues

Congos are hardy when their parameters are right but vulnerable when stressed. Watch for:

• Ich (white spot): classic stress disease. Raise temperature gradually to 82°F and treat with an ich medication from our fish medications collection.
• Fin damage: usually from nippy tank mates or rough décor. Identify the cause and treat with clean water.
• Pale color / hiding: almost always a school-size or water-parameter issue. Add more Congos or check parameters before reaching for medication.
• Bloat / stringy waste: usually overfeeding or a bad food batch. Fast for 48 hours and feed daphnia.

Where to Buy Congo Tetras

We carry healthy, quarantined Congo Tetras at our Cheyenne shop and ship them nationwide. Juveniles ship best and color up beautifully over their first year in your tank. Buy in groups of 6+ — both for the fish's sake and because we offer the best per-fish pricing on schooling quantities.

If you're stocking a new community tank, also check out our full tetras collection, beginner-friendly fish, and weekly new arrivals.

FAQ

Are Congo Tetras aggressive?
No. They're peaceful when kept in proper schools of 6+. Small groups can occasionally show stress-driven nipping, which is corrected by adding more Congos.

How many Congo Tetras should I keep together?
Minimum six. Eight to ten is much better. They're an obligate schooling species and don't thrive alone or in small groups.

What's the minimum tank size for Congo Tetras?
30 gallons is the practical floor for a school of 6. A 40-long or 55-gallon is much better and will let you keep 8–10 happily.

Can Congo Tetras live with bettas?
Not recommended. Congos are too active and too large; they'll stress a betta and bettas may flare and nip at male Congos' fins.

Do Congo Tetras eat shrimp?
Adults will eat cherry shrimp and juvenile shrimp. Amano shrimp are usually safe due to size but not guaranteed.

How long do Congo Tetras live?
Typically 4–6 years with good care. Some hit 8 in pristine conditions.

Why are my Congo Tetras pale?
Three likely causes: too-bright lighting, too-small school, or substrate that's too light-colored. Dark substrate, dim light, and 8+ fish solves most cases.

Do Congo Tetras need a planted tank?
Strongly recommended. Plants reduce stress, shade the tank, and dramatically improve their colors. They can survive in unplanted tanks but won't show their best.

Visit Us in Cheyenne

We hand-select and quarantine every fish that comes through our shop. Stop by our Cheyenne, WY store to see our current Congo Tetra stock and get personalized advice on stocking your tank — or shop online and we'll ship nationwide. Browse our full freshwater fish collection or best sellers to start building your tank.