TankStockingHow many Cardinal Tetra in a 15 gallon tank?
A 15-gallon (57 L) tank comfortably holds about 6–9 Cardinal Tetra as a single-species display — a conservative range that leaves room for tankmates and a margin for error.
Cardinal Tetra key facts
| Adult size | 3 cm |
|---|---|
| Minimum tank | 15 US gal |
| Minimum group | 6+ (shoal) |
| Temperament | Peaceful |
| Temperature range | 23–29°C |
| pH range | 4–7.5 |
| Bioload | Low |
| Swim level | Midwater |
| Beginner-friendly | Yes |
Sources & confidence (1 species)
This backs the Cardinal Tetra size, tank and group figures used here. Each figure is read from the TankStocking species database (v2026.06); below is the care reference behind it and how confident we are in that data. Confidence reflects the source quality, not whether any pairing is safe. Full source list and the welfare model are on the methodology page.
- Cardinal Tetra Paracheirodon axelrodi — Seriously Fish (seriouslyfish.com/species/paracheirodon-axelrodi) high confidence
TankStocking sizes this from a per-species footprint — the territory and waste a single Cardinal Tetra needs in a comfortable display tank — rather than the unreliable "inch per gallon" rule. On that basis a 15-gallon tank comfortably suits about 6–9 Cardinal Tetra. Keep a minimum of 6 — Cardinal Tetra is a social species that suffers in smaller groups. This is a comfortable display range, not a hard ceiling: stocking lighter keeps water quality stable and leaves headroom for tankmates and growth.
TankStocking's bio-load gauge alone would not flag a tank this size as over-stocked until roughly 25 Cardinal Tetra — but that is a model maximum, not the recommended number. It leaves no headroom for water-quality swings, tankmates, or growth, so treat 6–9 as the comfortable target.
They are gentle and easy to stock around, with the same one caveat as neons: keep them away from anything big enough to eat them. The engine clears small, peaceful community fish and flags larger predators. A big school in a planted tank is one of the hobby's great sights.
Want a community rather than a single-species tank? The Cardinal Tetra tank mates guide lists the species the engine clears with Cardinal Tetra.
9× Cardinal Tetra
✓ Good starter plan9× Cardinal Tetra
About 6–9 Cardinal Tetra is a comfortable display level for 15 gallons — fewer is always safer, and leaves headroom for tankmates.
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Common questions
How many Cardinal Tetra can I keep in a 15-gallon tank?
A 15-gallon (57 L) tank comfortably holds about 6–9 Cardinal Tetra as a single-species display — a conservative range that leaves room for tankmates and a margin for error.
What size tank do Cardinal Tetra need?
Cardinal Tetra need at least 15 US gallons, kept in a group of 6 or more. Bigger is better — more water means more stable parameters and more room to stock tankmates.
More on stocking Cardinal Tetra
Related guides on TankStocking — each scored by the same welfare engine as the planner.
Cardinal Tetra tankmates & community
Cardinal Tetra in other tank sizes
Stocking numbers are planning estimates — filtration, planting, and maintenance all shift the real ceiling. Cycle the tank and stock gradually. How this estimate works →