Should I buy it?
Congo Tetra
Phenacogrammus interruptus
Fishori provides conservative planning guidance, not guarantees.
Based on multiple reputable aquarium care sources with strong agreement. Use the numbers here as planning defaults — your room, water, and routine still shape real-world outcomes.
Large tetra at 8 cm with iridescent flanks and flowing fins on males. Needs a long tank with low flow and soft water. Males are spectacular in a mature school.
Best for
Planted tanks 180L or more with very soft slow-moving water and a school of six or more.
Avoid if
Your tank is under 120 cm long, water is hard alkaline, or you keep fin-nipping species.
Top things that go wrong
- Group welfare — not a solo display fish. Plan at least **8** together for normal behaviour; smaller groups often mean stress, colour loss, or nipping depending on species.
- Shrimp & snails. Shrimp: compatible in most setups. Cherry shrimp and other dwarf species coexist with peaceful small fish, though baby shrimp are food for almost any fish that gets to them.
Common mistakeStrong current in a Congo tetra tank. They come from slow forest streams; high flow damages their long fins and causes permanent stress.
What most shops don't tell you
- 1.Buying three or four to start. Congo Tetra settles in a group of 8 or more. An understocked school sulks at the back of the tank and loses colour within a fortnight.
- 2.Males develop long flowing fin extensions in stable water. The fins fray inside days when water quality slips. They are a live water-quality gauge in the tank, not just decoration.
About this species
Congos are large shy African characins, 6 to 9 cm adult, with long male fin extensions. Water quality and a long footprint matter. The fins fade first when maintenance slips.
- Diamond Tetra120L min · same group, similar adult size
- Serpae Tetra100L min · same fish family
- Black phantom tetra80L min · same fish family
- Columbian Tetra80L min · same group, similar adult size
- Penguin tetra80L min · same group, similar adult size
- Rosy Tetra80L min · same fish family
- Rummy Nose Tetra80L min · same group, similar adult size
- Splash tetra80L min · same group, similar adult size
- African freshwater butterflyfishalso intermediate peaceful, similar tank size
- Black ruby barbalso intermediate peaceful, similar tank size
- Boesemani Rainbowfishalso intermediate peaceful, similar tank size
- Bolivian Ramalso intermediate peaceful, similar tank size
- Brown / hockey-stick pencilfishalso intermediate peaceful, similar tank size
- Checkerboard cichlidalso intermediate peaceful, similar tank size
- African freshwater butterflyfish tank mateslists this fish as a safe and recommended mate
- Banded leporinus tank mateslists this fish as a safe and recommended mate
- Black ghost knifefish tank mateslists this fish as a safe and recommended mate
- Dwarf Neon Rainbowfish tank mateslists this fish as a safe and recommended mate
- Moonlight gourami tank mateslists this fish among its recommended pairings
- Opaline gourami tank mateslists this fish among its recommended pairings
- Penguin tetra tank mateslists this fish among its recommended pairings
- Pictus catfish tank mateslists this fish among its recommended pairings
Plan grid
Key limits are shown above; this section adds planning detail: pH band, swim level, bioload and activity, and the radar.
Swim zones
Planning trait chart
Six indices for comparing species on paper before you spend.
- Beginner ease32
- Peacefulness90
- Community fit83
- Small-tank fit93
- Hardiness54
- Energy86
Numbers are deterministic planning indices from Fishori fields — not a scientific score of your individual fish.
Common setup sketches
Conservative patterns from Fishori fields — still run the pair checker for every species you add; sketches are not a stocking guarantee.
Rough 180L+ layout: one calm centrepiece, 8–12 small tetras/rasboras, 6–8 corydoras-type bottom fish — verify every name in the pair checker before buying.
Safe directions on file include: Corydoras Catfish, Boesemani Rainbowfish, Dwarf Neon Rainbowfish.
Prioritise 8+ of Congo Tetra in 180L+ with filtration sized for messy feeding — add only mates that already pass pair checks with this species.
Tank mate intelligence
Peaceful schoolers (six minimum) for large planted community tanks with corydoras, rainbowfish, bolivian rams, and other calm similar-size species. Avoid nippy barbs like tiger and serpae that will shred long flowing fins. Skip any cichlid that views a 7 cm tetra as food.
Pair-level compatibility with this fish as anchor.
Read the blocking rule on each pair page before experimenting.
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: Congo Tetra + Corydoras Catfish
Behaviour, temperament, and what to watch
Prose and lists come from the same record: read temperament first, then glass-level signals so you are not surprised after day three.
Congo Tetra is peaceful in mixed company.
Stress / aggression triggers on file
- Sudden crowding
- Poor water quality
Fin nipping: Not a habitual fin-nipper, but individuals can still test fins under stress or in a crowded tank.
Predation: Not a predator toward similarly-sized community fish. The usual community caveats about mouth size still apply for very small fry or shrimp.
Territory: Not strongly territorial, but still claims a working area in the tank. Give it room to settle without overlapping the next species' patch.
Planted tanks: excellent — easy plant ideas
In the glass: typical and warning signs
- Busy at feeding time — expects food to hit the water predictably.
- Shoaling/schooling: most colour and confidence show when the group meets **8+**.
- Clamped fins, gasping at the surface, hiding non-stop, or refusing food after the first week.
- Rapid breathing when parameters swing — fix ammonia/nitrite first, then reassess mates.
- Low listed risk — still watch new introductions.
- Separate or rehome if injuries appear, one fish is pinned, or feeding becomes a daily chase.
- If water is stable but behaviour worsens, reduce stocking or remove the highest-impact species first.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Care parameters: water, food, inverts, grouping
Chemistry and group rules sit here so you are not re-reading the same line from tank mate or temperament blocks. Swim level is in the plan grid above.
Hardness
medium
Diet
omnivore
Mixed diet: a quality flake or pellet as the staple, with frozen or live foods two or three times a week.
Shrimp & snails
Shrimp: compatible in most setups. Cherry shrimp and other dwarf species coexist with peaceful small fish, though baby shrimp are food for almost any fish that gets to them.
Shoaling species. Buy 8 or more of one species together. Smaller schools sulk, lose colour, and redirect their schooling energy at whatever else is in the tank.
Egg scatterers and schoolers still spawn in stable tanks. Have a plan for the fry, or accept that the parents and tank mates will eat them in a community setup.
- Hold 23 to 28 °C steadily on a real thermometer, not the dial on the heater.
- Aim for pH 6 to 7.5 and a hardness you can re-test in two weeks. A one-time strip in the shop car park is not a water test.
- Schooling species. Buy 8 or more from the same tank on the same day before adding any centrepiece fish.
- Tank volume meets or exceeds 180L published minimum for adults.
- You can stock at least 8 individuals (group welfare).
- Heater can hold 23–28°C without cooking cooler-water tank mates.
- No known fin-nippers paired with long-finned fish unless you accept documented risk.
Explore and stocking hubs
Same library as the rest of Fishori: tank-mate index for this species, category peers, guides, and litre-based stocking lists where min tank on file is within the hub volume.
Plan with tools
Pair-level rules and multi-fish stocking use the same conservative engine — add this fish in the tank builder only after mates pass pair checks.
Filtration & heating
A 180L minimum tank needs a filter rated for at least 720L/hr turnover and a heater to hold 23–28°C reliably.
Plant suggestions
Congo Tetra does well in planted tanks. Plants compatible with 23–28°C and pH 6–7.5:
Profile status: partially verified · Evidence tier: high · 3 linked source(s). Fishori does not fabricate citations.
Fishori uses conservative planning rules based on these sources.
Confidence is explained in the summary at the top of this page (same tier as here), not repeated below.
How Fishori evaluates compatibility (same logic as pair and tank tools).
- Seriously Fish. Phenacogrammus interruptus
Primary: aquarium size, water chemistry, behaviour, and compatibility (URL verified in upgrade script; recheck if site content changes).
- FishBase. Phenacogrammus interruptus
Secondary: taxonomy, distribution, and maximum length in nature; cross-check with aquarium import lines and measured tank parameters.
- Wikipedia. Phenacogrammus interruptus
Secondary: general species context; verify all husbandry numbers against a dedicated aquarium care sheet and your test kit, not a single table row.
Evidence notes
- The Seriously Fish profile for the binomial in this record was successfully reached as the primary aquarium reference.
- FishBase contributes natural-range size and habitat context. Translate those numbers through your heater, your water report, and your tank footprint before stocking.
- Wikipedia is only cited if the article URL returned OK. Use it for orientation, not as the only care sheet for an import.
- All compatibility text reflects typical hobby experience and the Fishori model. Individual fish, shop stress, and the order tank mates are added in can still defy a single-paragraph label.
- Fishori profiles work from typical aquarium trade sizes and hobby care norms. Specialist site checks and literature review for this species are not yet recorded here, so the ranges on this page are planning numbers rather than guarantees.