Cardinal Tetra and Betta: Can They Live Together?
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Side-by-side comparison
| Factor | Cardinal Tetra | Betta | Assessment |
|---|---|---|---|
| Water temperature | 73–81°F | 76–82°F | Overlap 76–81°F |
| pH | 5.5–7 | 6.5–7.5 | Overlap 6.5–7 |
| Hardness | 1–8 dGH | 3–15 dGH | Overlap 3–8 dGH |
| Adult size | 2.0″ | 2.5″ | Similar |
| Temperament | Peaceful | Aggressive | Aggression risk |
| Swim level | Mid | Top | Different zones |
| Minimum tank | 20 gal | 5 gal | Together: 23 gal+ |
Shared water parameters
- Temperature both tolerate: 76–81°F
- pH both tolerate: 6.5–7
- Hardness both tolerate: 3–8 dGH
- Recommended combined tank: 23 gallons or larger
Risks and things to watch
Territorial aggression
Betta defends territory and will chase. Long tanks with broken sight lines reduce this; small square tanks make it worse.
Group requirements
Compatibility is not only about the two species getting along — each still needs its own social setup met inside the same tank.
- Cardinal Tetra — minimum group of 6. Budget tank space for the whole shoal, not one fish.
- Betta — one per tank only.
Frequently asked questions
Can cardinal tetra and betta live together?
Possible, with conditions. Cardinal Tetra and Betta can work, but this is a conditional yes rather than easy one. Read the risk section below before buying — the pairing usually fails for one specific reason, not because of general incompatibility. Plan on 23 gallons minimum.
What size tank do cardinal tetra and betta need together?
Plan for at least 23 gallons. Cardinal Tetra alone needs 20 gallons and Betta needs 5, but combined stocking needs headroom for filtration and swimming space, not just volume.
What temperature suits both species?
Both are comfortable between 76 and 81°F. Set the heater to the middle of that window and keep it stable.
What pH works for both?
Aim for pH 6.5–7, which sits inside both species' comfortable range.
Will betta eat cardinal tetra?
Unlikely. At 2.5″ versus 2.0″ the size gap is not large enough for predation, though fry and juveniles are never safe in a community tank.
How should the tank be arranged?
Use plants, wood and rock to break sight lines, keep open swimming space along the front, and add the more territorial species last so it cannot claim the whole tank before the other settles in.
Explore further
Assessment generated from our compatibility methodology: parameter overlap, adult size ratio, temperament and swimming zone. Reviewed by Marcus Rivera.