Congo Tetra
Phenacogrammus interruptus
Min Tank Size
115L
Adult Size
8.5 cm
Lifespan
5 years
School Size
6+
About
Originating from the Congo River basin in central Africa, Phenacogrammus interruptus is one of the most visually impressive tetras you can keep. Males are genuinely stunning, covered in iridescent scales that shift between blue, gold, and green depending on the light, with long flowing extensions on the dorsal, caudal, and anal fins that trail behind them as they swim. Females are smaller, plainer, and lack the fin extensions, but still carry a warm golden sheen.
5cm as adults, which surprises people who compare it to neons or cardinals. They need a proper 115-liter minimum, and honestly a longer footprint tank serves them better than a tall one since they're active midwater swimmers. Water conditions should lean toward the soft and slightly acidic side to match their native Congo basin habitat, though they adapt reasonably well to neutral pH.
They're not fussy eaters and will take flakes, pellets, frozen bloodworms, brine shrimp, and daphnia without complaint. Temperament is peaceful, and they're genuinely one of the better large tetras for a community setup.
Keep at least six, ideally more, and you'll see their best colors and most relaxed behavior. A single male in a large group is a showpiece fish.
If you want to see how stunning a mature male looks in a planted blackwater setup, browsing real tank builds from hobbyists who specialize in African biotopes is worth your time.
Water Parameters
Temperature
°CpH
GH
dGHKH
dKHSwimming Level
Flow Preference
Keeping multiple Congo Tetra together
Congo Tetra are shoaling fish and need company of their own kind. Keep a group of at least 6. Smaller groups leave them stressed, washed-out in color, and prone to hiding.
Compatibility
Congo tetras work well with other large, peaceful midwater fish. Good matches include larger rasboras, rainbowfish, peaceful cichlids like keyhole or angelfish (with caution given the flowing fins), and other mid-to-large tetras. Avoid tiger barbs, serpae tetras, or any confirmed fin nippers since the males' trailing fins are an easy target. Bottom dwellers like cory catfish, plecos, and kuhli loaches are excellent companions. Dwarf shrimp are a risk, especially juveniles. Larger shrimp like amanos generally hold their own, but small neocaridina colonies may take losses over time.
Commonly kept with
Species this one is most often paired withCommonly tried but avoid
Often paired, but shouldn't beCare Notes
The most common mistake is keeping them in a tank that's too small or in a group that's too small. Under six fish, they get stressed and colors wash out badly. They also need soft, warm water to look their best. Hard alkaline water won't kill them but males won't develop the full fin extensions or intense coloration you see in photos. Diet variety matters too. Dry food alone is fine for maintenance, but regular frozen or live foods bring out color and condition noticeably.
Behavior & Aggression
Congo tetras are peaceful fish and rarely cause problems in a community tank. Males can show mild posturing toward each other, particularly when competing for female attention, but this almost never escalates to real damage. The bigger concern is going the other direction: their long flowing fins make them targets for fin-nipping species, not the other way around. Keeping a proper group of six or more significantly reduces any low-level chasing between males and keeps the school settled and confident.
Things to Know
- Males develop spectacular trailing fins that are easily nipped by fin-nipping species.
- Needs a long tank for swimming, not just a tall one.
- Keep 6 or more or they'll be skittish and colors will fade.
- May eat very small dwarf shrimp (under 2cm).
- Can be skittish and may jump, keep a tight lid.
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