Can Black Skirt Tetra live with Molly?
Case-by-case. Watch group sizes, tank size, and feeding zones.
Why Black Skirt Tetra and Molly Don't Make an Easy Pair
They can coexist, but you need to manage the setup carefully. The temperament combination (semi-aggressive+peaceful) can work, but you will need to watch them at feeding time for the first week.
Black Skirt Tetra
Gymnocorymbus ternetzi
| Adult Size: | 2.5" |
| Temperament: | semi-aggressive |
| Min Tank: | 15 gal |
| Temperature: | 68-79°F |
| pH Range: | 6.0-7.5 |
Molly
Poecilia sphenops
| Adult Size: | 4.5" |
| Temperament: | peaceful |
| Min Tank: | 20 gal |
| Temperature: | 72-82°F |
| pH Range: | 7.0-8.0 |
Water Parameter Overlap
| Parameter | Black Skirt Tetra | Molly | Overlap |
|---|---|---|---|
| Temperature | 68-79°F | 72-82°F | 7°F ✓ |
| pH | 6.0-7.5 | 7.0-8.0 | 0.5 ✓ |
Compatibility Breakdown
Temperament Match: semi-aggressive + peaceful. Semi-aggressive → watch territory and feeding.
⚠️ Size Predation Risk: Black Skirt Tetra (2.5") vs Molly (4.5"). A 2.0" gap — the larger fish will view the smaller fish as food.
Score: 70.0/100 (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 79°F.
- pH: maintain 7.0 – 7.5.
- Hiding spots: essential for Black Skirt 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:
Quiet internal filter for 20-gallon tanks
Explore Related Checks
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Accuracy note: This tool uses expert rules + FishBase.org data. Individual fish behavior varies — a semi-aggressive individual Black Skirt 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.