Compatibility Overview
Cardinal Tetra and Fire Eel are generally not recommended to be housed together. The issues listed above — whether water parameter incompatibility, predation risk, or aggression — create conditions where one or both fish are likely to suffer harm or chronic stress.
| Factor | Cardinal Tetra | Fire Eel | Verdict |
|---|---|---|---|
| Temperature | 73–82°F | 75–82°F | ✅ 75–82°F |
| pH Range | 4.5–7.0 | 6.0–7.0 | ✅ 6.0–7.0 |
| Temperament | peaceful | aggressive | ❌ Risk |
| Adult Size | 1.5 in | 19.7 in | ❌ 13× difference |
| Min. Group | 6+ | 1+ | See below |
| Min. Tank Size | 100 gallons (for both species) | — | |
✅ Compatibility Positives
❌ Incompatibility Reasons
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
Fire Eel — Aquarium species
The Fire Eel is a stunning, red-bottomed species that requires a spacious tank. They are peaceful bottom feeders and do best in a well-planted, mature aquarium. With a moderate activity level, they can be a great addition to a community tank, but their size and diet may be incompatible with smaller fish. Regular water changes and careful tank management are
Frequently Asked Questions
Can Cardinal Tetra live with Fire Eel?
Generally not recommended. Cardinal Tetra and Fire Eel are generally not recommended to be housed together. The issues listed above — whether water parameter incompatibility, predation risk, or aggression — create conditions where one or both fish are likely to suffer harm or chronic stress.
What tank size do I need for Cardinal Tetra and Fire Eel together?
A minimum of 100 gallons is recommended for keeping Cardinal Tetra and Fire Eel together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Cardinal Tetra and Fire Eel?
75–82°F
Is a Cardinal Tetra aggressive toward a Fire Eel?
Cardinal Tetra is peaceful and Fire Eel is aggressive. The adult size gap creates a meaningful predation risk.
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 | 100/100 |
| Ph | 100/100 |
| Temperament | 30/100 |
| Adult Size | 8/100 |
| Swim Zone | 92/100 |
| 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 | 100 gal | Only for the recommended minimum groups, mature filtration, and close monitoring. |
| Recommended community | 150 gal | Adds territory, swimming room, and a safer buffer for behavior. |
| Low-conflict setup | 220 gal | Best when keeping larger schools or reducing territorial pressure. |