Neon tetra vs cardinal tetra
Two nearly identical blue-and-red tetras sit side by side in the shop. Which one suits your tank?
Short answer
The cardinal is larger, warmer-water and softer-water, with red running the whole length of the body. The neon is cheaper, tolerates a wider temperature range, and — despite its reputation — is the less robust of the two as farmed stock.
Side by side
| Dimension | Neon tetra | Cardinal tetra | Favours |
|---|---|---|---|
| Red stripe | Rear half only | Full body length | — |
| Adult size | 3–3.5 cm | 4–5 cm | — |
| Temperature | 20–26 °C | 24–30 °C | Neon tetra |
| pH | 4.0–7.5 | 4.0–7.0 | Neon tetra |
| Hardness | 1–10 °dGH | 1–6 °dGH | Neon tetra |
| Source | Almost entirely farmed | Largely wild-caught | Neither |
| Robustness of trade stock | Variable; heavily line-bred | Wild stock arrives stressed but is genetically sound | Neither |
| Price | Lower | Higher | Neon tetra |
| Minimum group | 8 | 8 | — |
Which to choose
Neon tetra
Choose the neon if your tank runs at 24 °C or below, if you want the cheaper option, or if you are keeping it alongside species that will not tolerate 27 °C.
Cardinal tetra
Choose the cardinal if your tank is warm and your water is soft, if you want the stronger colour, and if you are prepared to quarantine wild-caught stock.
One caveat
Neither is a good first fish for a tank that has just finished cycling. Both are sensitive to ammonia and nitrite, and both are frequently sold as hardy beginners' fish on the strength of their price rather than their biology.