Can Molly live with Rummy-Nose Tetra?
Case-by-case. Watch group sizes, tank size, and feeding zones.
Why Molly and Rummy-Nose Tetra Don't Make an Easy Pair
They can coexist, but you need to manage the setup carefully. The temperament combination (peaceful+peaceful) can work, but you will need to watch them at feeding time for the first week.
Molly
Poecilia sphenops
| Adult Size: | 4.5" |
| Temperament: | peaceful |
| Min Tank: | 20 gal |
| Temperature: | 72-82°F |
| pH Range: | 7.0-8.0 |
Rummy-Nose Tetra
Hemigrammus rhodostomus
| Adult Size: | 2.0" |
| Temperament: | peaceful |
| Min Tank: | 20 gal |
| Temperature: | 75-82°F |
| pH Range: | 5.5-7.0 |
Water Parameter Overlap
| Parameter | Molly | Rummy-Nose Tetra | Overlap |
|---|---|---|---|
| Temperature | 72-82°F | 75-82°F | 7°F ✓ |
| pH | 7.0-8.0 | 5.5-7.0 | No overlap ✗ |
Compatibility Breakdown
Temperament Match: peaceful + peaceful. Both peaceful → minimal conflict.
⚠️ Size Predation Risk: Molly (4.5") vs Rummy-Nose Tetra (2.0"). A 2.5" gap — the larger fish will view the smaller fish as food.
Score: 70/100 (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 75°F and 82°F.
- pH: no shared range. One species will be outside its tolerance regardless of what you set.
- Hiding spots: essential for Molly — 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
See what else works with these fish:
Accuracy note: This tool uses expert rules + FishBase.org data. Individual fish behavior varies — a peaceful individual Molly 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.