Compatibility Overview
Cardinal Tetra and Keyhole Cichlid can potentially coexist, but the combination requires careful attention. Some combination of water parameter differences, size mismatch, or temperament issues make this pair challenging. A larger tank (minimum 40 gallons), dense planting, and close monitoring are essential.
| Factor | Cardinal Tetra | Keyhole Cichlid | Verdict |
|---|---|---|---|
| Temperature | 73–82°F | 72–79°F | ✅ 73–79°F |
| pH Range | 4.5–7.0 | 7.0–8.0 | ⚠️ 7.0–7.0 (narrow) |
| Temperament | peaceful | semi | ⚠️ Monitor |
| Adult Size | 1.5 in | 2.0 in | ✅ Similar |
| Min. Group | 6+ | 1+ | 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
Keyhole Cichlid — Aquarium species
The Keyhole Cichlid is a popular choice for beginners due to its relatively easy care and peaceful temperament. These fish are known for their distinct keyhole marking and vibrant coloration. They do well in a community tank with other peaceful species, but should be provided with plenty of hiding spots to feel secure. With proper care, they can live for sev
Frequently Asked Questions
Can Cardinal Tetra live with Keyhole Cichlid?
With significant caution and a larger tank. Cardinal Tetra and Keyhole Cichlid can potentially coexist, but the combination requires careful attention. Some combination of water parameter differences, size mismatch, or temperament issues make this pair challenging. A larger tank (minimum 40 gallons), dense planting, and close monitoring are essential.
What tank size do I need for Cardinal Tetra and Keyhole Cichlid together?
A minimum of 40 gallons is recommended for keeping Cardinal Tetra and Keyhole Cichlid together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Cardinal Tetra and Keyhole Cichlid?
73–79°F
Is a Cardinal Tetra aggressive toward a Keyhole Cichlid?
Cardinal Tetra is peaceful and Keyhole Cichlid is semi. Their preferred pH ranges are difficult to reconcile.
Related Compatibility Guides
Compatibility score breakdown
The overall score is weighted across water chemistry, behavior, adult size, swimming zone, and social needs. A score is a planning aid—not a guarantee for individual fish.
| Factor | Score |
|---|---|
| Temperature | 86/100 |
| Ph | 0/100 |
| Temperament | 75/100 |
| Adult Size | 100/100 |
| Swim Zone | 68/100 |
| Social Needs | 92/100 |
Tank size scenarios
Use the scenario that matches the actual group sizes and temperament you plan to keep.
| Scenario | Tank | When it applies |
|---|---|---|
| Minimum viable | 40 gal | Only for the recommended minimum groups, mature filtration, and close monitoring. |
| Recommended community | 55 gal | Adds territory, swimming room, and a safer buffer for behavior. |
| Low-conflict setup | 90 gal | Best when keeping larger schools or reducing territorial pressure. |