TankStockingHow many Neon Tetra in a 40 gallon tank?
A 40-gallon (151 L) tank comfortably holds about 17–25 Neon Tetra as a single-species display — a conservative range that leaves room for tankmates and a margin for error.
Neon Tetra key facts
| Adult size | 3 cm |
|---|---|
| Minimum tank | 10 US gal |
| Minimum group | 6+ (shoal) |
| Temperament | Peaceful |
| Temperature range | 21–25°C |
| pH range | 5–7.5 |
| Bioload | Low |
| Swim level | Midwater |
| Beginner-friendly | Yes |
Sources & confidence (1 species)
This backs the Neon 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.
- Neon Tetra Paracheirodon innesi — Seriously Fish (seriouslyfish.com/species/paracheirodon-innesi) high confidence
TankStocking sizes this from a per-species footprint — the territory and waste a single Neon Tetra needs in a comfortable display tank — rather than the unreliable "inch per gallon" rule. On that basis a 40-gallon tank comfortably suits about 17–25 Neon Tetra. Keep a minimum of 6 — Neon 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 67 Neon Tetra — but that is a model maximum, not the recommended number. It leaves no headroom for water-quality swings, tankmates, or growth, so treat 17–25 as the comfortable target.
The main risk for a neon tetra is being eaten: anything large enough to fit a 3 cm fish in its mouth is a problem, which is why angelfish and other bigger predators are flagged. Kept in a tight school of six or more with similarly-sized, peaceful tankmates, neons are one of the easiest community fish to stock around.
Want a community rather than a single-species tank? The Neon Tetra tank mates guide lists the species the engine clears with Neon Tetra.
25× Neon Tetra
✓ Good starter plan25× Neon Tetra
About 17–25 Neon Tetra is a comfortable display level for 40 gallons — fewer is always safer, and leaves headroom for tankmates.
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Common questions
How many Neon Tetra can I keep in a 40-gallon tank?
A 40-gallon (151 L) tank comfortably holds about 17–25 Neon Tetra as a single-species display — a conservative range that leaves room for tankmates and a margin for error.
What size tank do Neon Tetra need?
Neon Tetra need at least 10 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 Neon Tetra
Related guides on TankStocking — each scored by the same welfare engine as the planner.
Neon Tetra tankmates & community
Neon 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 →