Can Red-Eye Tetra live with Swordtail?
Case-by-case. Watch group sizes, tank size, and feeding zones.
Why Red-Eye Tetra and Swordtail Don't Make an Easy Pair
They can coexist, but you need to manage the setup carefully. The temperament combination (peaceful+semi-aggressive) can work, but you will need to watch them at feeding time for the first week.
Red-Eye Tetra
Moenkhausia sanctaefilomenae
| Adult Size: | 2.75" |
| Temperament: | peaceful |
| Min Tank: | 20 gal |
| Temperature: | 72-82°F |
| pH Range: | 6.0-7.5 |
Swordtail
Xiphophorus helleri
| Adult Size: | 5.0" |
| Temperament: | semi-aggressive |
| Min Tank: | 20 gal |
| Temperature: | 72-78°F |
| pH Range: | 7.0-8.0 |
Water Parameter Overlap
| Parameter | Red-Eye Tetra | Swordtail | Overlap |
|---|---|---|---|
| Temperature | 72-82°F | 72-78°F | 6°F ✓ |
| pH | 6.0-7.5 | 7.0-8.0 | 0.5 ✓ |
Compatibility Breakdown
Temperament Match: peaceful + semi-aggressive. Semi-aggressive → watch territory and feeding.
⚠️ Size Predation Risk: Red-Eye Tetra (2.75") vs Swordtail (5.0"). A 2.2" gap — the larger fish will view the smaller fish as food.
Score: 60.0/100 (GOOD ≥80, CAUTION ≥50, RISKY <50).
🔧 Tank Setup Requirements (for Both)
- Minimum tank: 20 gallons — sized for the larger fish in the pair.
- Temperature: keep it between 72°F and 78°F.
- pH: maintain 7.0 – 7.5.
- Hiding spots: essential for Red-Eye Tetra — caves, plants, or driftwood to retreat when feeling stressed.
- Water changes: 25% weekly minimum. Two species mean double the bioload.
🔧 Tank Stocking Calculator
Enter tank size to calculate safe stocking levels:
Recommended Equipment
Based on tank size 20+ gallons:
Tropical flake food for schooling tetras
Explore Related Checks
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Accuracy note: This tool uses expert rules + FishBase.org data. Individual fish behavior varies — a peaceful individual Red-Eye Tetra may act differently from its species average. Always observe, quarantine new arrivals for 2-4 weeks, and avoid overcrowding. If a pairing says CAUTION, start with a smaller group and a lid.