Should I buy it?
Congo Tetra
Phenacogrammus interruptus
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.
Congo Tetra tank mates · 200L tank size hub
peaceful · intermediate care
Sources & confidencehigh · partially verified · beginner: caution
Checked against several solid care sources that mostly agree. Numbers here are a careful starting point. Your tap water, tank size, and habits decide the rest. How we evaluate.
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.
Common mistakeRunning strong current in a Congo tetra tank is how keepers invent exhausted, washed-out fish that never settle. They come from slower forest streams. Soften flow, give open midwater, and keep eight or more — a high-flow African cichlid layout is the wrong template for this 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. Cherry shrimp and other dwarfs can coexist with peaceful small fish; baby shrimp are food for almost anything that finds them.
What most shops don't tell you
- 1.Myth: Congo tetras thrive in any high-flow African-style community as hardy dither fish. Reality: they prefer softer, calmer midwater with a real school of eight or more — strong current and token numbers leave them stressed, colourless, and constantly pacing.
- 2.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.
- 3.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.
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- Rosy Tetra80L min · same fish family
- Rummy Nose Tetra80L min · same group, similar adult size
- Splash tetra80L min · same group, similar adult size
- Beckford Pencilfish60L min · same fish family
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- Checkerboard cichlidalso intermediate peaceful, similar tank size
- African freshwater butterflyfish tank matesnames this fish as a conditional pairing — read the pair page conditions
- Banded leporinus tank matesnames this fish as a conditional pairing — read the pair page conditions
- Black ghost knifefish tank matesnames this fish as a conditional pairing — read the pair page conditions
- 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 matesnames this fish as a conditional pairing — read the pair page conditions
- 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 above. Here: pH band, swim level, bioload, and activity.
Swim zones
Care snapshot
Quick compare before you buy. Not a score of how “good” the fish is.
- 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.
Example setups
Starting points only. Run the pair checker for every fish you add.
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.
Safer directions include: Boesemani Rainbowfish, Bolivian Ram, Corydoras Catfish.
Prioritise 8+ of Congo Tetra in 180L+ with filtration sized for messy feeding — add only mates that already pass pair checks with this species.
Compatibility
Tank mates for Congo Tetra
Usually safer (engine GOOD): Boesemani Rainbowfish, Bolivian Ram, Corydoras Catfish, Dwarf Neon Rainbowfish. Conditional (CAUTION — read the pair page before buying): Serpae Tetra, Tiger Barb. Avoid (RISKY): Jack Dempsey, Oscar. Every name links to a live pair check — the lists are a shortlist, not a stocking plan.
Usually safer
Open a pair page with this fish as the starting point.
Needs planning
Read the blocking rule on each pair page before experimenting.
Usually avoid
Do-not-stock combinations on conservative hobby rules.
Compare with
Run a real pair check: Congo Tetra + Boesemani Rainbowfish
Behaviour and temperament
Congo tetras are peaceful schoolers that stay calmer in groups of eight or more with open swim space. They do not bully robust neighbours. Stress shows as fading, clamped fins, and skittish pacing when under-grouped or blasted by excessive flow.
What sets them off
- Sudden crowding
- Poor water quality
Fin nipping: Not a habitual fin-nipper; stressed or crowded individuals can still test fins.
Predation: Not a predator toward similarly sized community fish; fry and dwarf shrimp are still fair game for most species.
Territory: Not strongly territorial, but still needs room so its working space does not overlap the next fish.
Planted tanks: excellent — easy plant ideas
In the glass: typical and warning signs
- Eight or more hold midwater as a shimmering school in softish open water.
- Males flash longer fins when the group feels secure after lights soften.
- Pacing against a powerhead means flow and footprint failed before diet.
- A faded handful needs more of their own kind before a different staple.
- Low listed risk as aggressors.
- Fin-nippers and large cichlids are the usual failure modes — not Congo malice.
- Reduce flow and grow the school before chasing mystery disease only.
- Remove nippy barbs at the first torn fin.
Fish behaviour can vary between individuals and tank setups. Always observe new fish closely after introduction.
Water, food, and grouping
Hardness
medium
Diet
omnivore
Congo tetras are midwater omnivores that take quality flake or micro-pellets plus frozen foods in a school of eight or more. Protein-only feeding without plant matter leaves colour flat, and food that never reaches the midwater school leaves them thin. Feed deliberately in open water with softish chemistry and expect males to show when the school feels secure.
Shrimp & snails
Cherry shrimp and other dwarfs can coexist with peaceful small fish; baby shrimp are food for almost anything that finds them.
Schooling species — buy 8+ together. Smaller groups stress and lose colour.
- 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
Tank-mates hub, matching guides, category peers, and litre stocking lists around this species’ minimum tank.
Plan with tools
Check mates as pairs first, then add this fish in the tank builder for the full stocking.
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:
Research: partially verified · Confidence: high · 3 linked source(s). We do not invent citations.
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.
Featured compatibility checks
Curated pair pages for Congo Tetra. Each opens a full verdict — not just a list label.
Common questions about Congo Tetra
- How big do Congo Tetra get?
- Congo Tetra adults run about 6–9 cm. In home tanks they usually land near 8 cm — plan space and filtration for that, not the juvenile in the shop bag.
- What size tank does Congo Tetra need?
- 180L is the planning floor for adult swimming space and bioload. A 240L+ tank is the more comfortable long-term footprint. Length and depth matter as much as raw litres for active or territorial fish.
- Are Congo Tetra aggressive?
- Congo tetras are peaceful schoolers that stay calmer in groups of eight or more with open swim space. They do not bully robust neighbours. Stress shows as fading, clamped fins, and skittish pacing when under-grouped or blasted by excessive flow.
- Do Congo Tetra need to be kept in a group?
- Schooling species — buy 8+ together. Smaller groups stress and lose colour.
- What is the most common mistake with Congo Tetra?
- Running strong current in a Congo tetra tank is how keepers invent exhausted, washed-out fish that never settle. They come from slower forest streams. Soften flow, give open midwater, and keep eight or more — a high-flow African cichlid layout is the wrong template for this species.
- What fish can live with Congo Tetra?
- The Congo Tetra profile lists Boesemani Rainbowfish, Bolivian Ram, Corydoras Catfish, Dwarf Neon Rainbowfish among its safer pairings (engine-checked GOOD). Serpae Tetra, Tiger Barb are conditional (CAUTION): workable only with the specific conditions on each pair page. Avoid Jack Dempsey, Oscar (RISKY). Run the pair checker for your exact water and tank size before stocking.