Compatibility Overview
Cardinal Tetra and Harlequin Rasbora can generally share an aquarium with appropriate planning. Both species prefer overlapping temperature and pH ranges, and neither poses a major aggression risk to the other. A minimum 40-gallon tank is recommended to provide adequate territory and water volume for both species.
| Factor | Cardinal Tetra | Harlequin Rasbora | Verdict |
|---|---|---|---|
| Temperature | 73–82°F | 72–81°F | ✅ 73–81°F |
| pH Range | 4.5–7.0 | 5.5–7.5 | ✅ 5.5–7.0 |
| Temperament | peaceful | peaceful | ✅ Compatible |
| Adult Size | 1.5 in | 1.75 in | ✅ Similar |
| Min. Group | 6+ | 8+ | See below |
| Min. Tank Size | 40 gallons (for both species) | — | |
✅ Compatibility Positives
⚠️ Caution Points
Species Profiles
Cardinal Tetra — Paracheirodon axelrodi
Brilliant red-and-blue schooling fish from the Rio Negro. Prefers soft, acidic, warm water — a natural companion for discus.
→ Full Cardinal Tetra care guide
Harlequin Rasbora — Trigonostigma heteromorpha
Active mid-level schooling fish with a distinctive black triangular patch. One of the best all-around community tank fish.
Frequently Asked Questions
Can Cardinal Tetra live with Harlequin Rasbora?
Yes, in a well-planned setup. Cardinal Tetra and Harlequin Rasbora can generally share an aquarium with appropriate planning. Both species prefer overlapping temperature and pH ranges, and neither poses a major aggression risk to the other. A minimum 40-gallon tank is recommended to provide adequate territory and water volume for both species.
What tank size do I need for Cardinal Tetra and Harlequin Rasbora together?
A minimum of 40 gallons is recommended for keeping Cardinal Tetra and Harlequin Rasbora together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Cardinal Tetra and Harlequin Rasbora?
73–81°F
Is a Cardinal Tetra aggressive toward a Harlequin Rasbora?
Cardinal Tetra is peaceful and Harlequin Rasbora is peaceful. No major aggression issues are expected between these species.