Should I buy it?
Cardinal Tetra
Paracheirodon axelrodi
Also known as: cardinal, large neon (trade), Cardinal, Large neon (trade)
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.
More demanding than neons. They need soft, acidic water in a settled tank three months old or more. The colour repays the wait.
Best for
Aquarists with soft water (RO mix, rainwater, or naturally low TDS) running a planted, mature community tank.
Avoid if
Your tap water is hard and alkaline, the tank is under three months old, or your stock includes larger predators.
Top things that go wrong
- Group welfare — not a solo display fish. Plan at least **6** together for normal behaviour; smaller groups often mean stress, colour loss, or nipping depending on species.
- Specialist husbandry. Ten or more for the colour to settle. Six is the absolute floor. Below that they wash out and hide.
- 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 mistakeSmall groups in hard or bright water. Cardinals need soft, dimmer conditions and a real school.
What most shops don't tell you
- 1.Keeping only three or four cardinals in a small bright tank. They lose colour and hide, especially in harder water.
- 2.Mixing with mollies, swordtails, or hard-water African cichlids without a split-tank or compromise plan.
- 3.More sensitive than neons. They want a tank that has been running three months or more, with soft acidic water that does not drift week to week.
About this species
Similar to the neon tetra but the red stripe runs the full body length. Cardinals are soft-water Rio Negro fish, fussier than neons about parameters.
- Beckford Pencilfish60L min · same group, comparable tank size
- Black Neon Tetra60L min · same group, comparable tank size
- Bloodfin tetra60L min · same group, comparable tank size
- Glowlight Tetra60L min · same group, comparable tank size
- Green neon tetra60L min · same group, comparable tank size
- Lemon Tetra60L min · same group, comparable tank size
- Silver Tip Tetra60L min · same group, comparable tank size
- X-ray tetra60L min · same group, comparable tank size
- Adolfoi coryalso intermediate peaceful, similar tank size
- Bamboo Shrimpalso intermediate peaceful, similar tank size
- Black ruby barbalso intermediate peaceful, similar tank size
- Brown / hockey-stick pencilfishalso intermediate peaceful, similar tank size
- Celebes Rainbowfishalso intermediate peaceful, similar tank size
- Celestial Pearl Danioalso intermediate peaceful, similar tank size
- Apistogramma Borellii tank mateslists this fish as a safe and recommended mate
- Apistogramma Macmasteri tank mateslists this fish as a safe and recommended mate
- Apistogramma Trifasciata tank mateslists this fish as a safe and recommended mate
- Beckford Pencilfish tank mateslists this fish as a safe and recommended mate
- Checkerboard cichlid tank mateslists this fish as a safe and recommended mate
- Discus tank mateslists this fish as a safe and recommended mate
- German Blue Ram tank mateslists this fish as a safe and recommended mate
- Marbled Hatchetfish tank mateslists this fish as a safe and recommended mate
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 ease59
- Peacefulness90
- Community fit83
- Small-tank fit100
- Hardiness57
- Energy54
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 90L+ 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, Harlequin Rasbora, German Blue Ram.
Prioritise 6+ of Cardinal Tetra in 60L+ with filtration sized for messy feeding — add only mates that already pass pair checks with this species.
Tank mate intelligence
Pairs well with corydoras, otocinclus, dwarf cichlids (apistogramma, German blue rams), discus, and other soft-water tetras.
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: Cardinal 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.
Peaceful and tightly shoaling. But they hide and lose colour when the school is small or the tank is new and unstable.
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
- Moderate pacing — not hyperactive, not motionless.
- Shoaling/schooling: most colour and confidence show when the group meets **6+**.
- 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
soft
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.
Ten or more for the colour to settle. Six is the absolute floor. Below that they wash out and hide.
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 27 °C steadily on a real thermometer, not the dial on the heater.
- Aim for pH 5.5 to 7 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 6 or more from the same tank on the same day before adding any centrepiece fish.
- Tank volume meets or exceeds 60L published minimum for adults.
- You can stock at least 6 individuals (group welfare).
- Heater can hold 23–27°C without cooking cooler-water tank mates.
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 60L minimum tank needs a filter rated for at least 240L/hr turnover and a heater to hold 23–27°C reliably.
Plant suggestions
Cardinal Tetra does well in planted tanks. Plants compatible with 23–27°C and pH 5.5–7:
Profile status: verified · Evidence tier: high · 4 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. Paracheirodon axelrodi
Primary: aquarium size, water chemistry, behaviour, and compatibility (URL verified in upgrade script; recheck if site content changes).
- FishBase. Paracheirodon axelrodi
Secondary: taxonomy, distribution, and maximum length in nature; cross-check with aquarium import lines and measured tank parameters.
- Wikipedia. Paracheirodon axelrodi
Secondary: general species context; verify all husbandry numbers against a dedicated aquarium care sheet and your test kit, not a single table row.
- Wikipedia. Paracheirodon axelrodi (cardinal tetra)
Encyclopaedia overview; use specialist aquarium sources for your stock's real temperature/pH/footprint needs.
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.