Can Goldfish live with Molly?
High risk due to water mismatch, aggression, or predation.
Why Goldfish and Molly Don't Make an Easy Pair
The size gap is 5.5" — Goldfish (10.0") and Molly (4.5"). A fish that fits in another fish's mouth will eventually end up there.
Goldfish
Carassius auratus
| Adult Size: | 10.0" |
| Temperament: | peaceful |
| Min Tank: | 30 gal |
| Temperature: | 62-74°F |
| pH Range: | 6.5-7.5 |
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 | Goldfish | Molly | Overlap |
|---|---|---|---|
| Temperature | 62-74°F | 72-82°F | 2°F ✓ |
| pH | 6.5-7.5 | 7.0-8.0 | 0.5 ✓ |
Compatibility Breakdown
Temperament Match: peaceful + peaceful. Both peaceful → minimal conflict.
⚠️ Size Predation Risk: Goldfish (10.0") vs Molly (4.5"). A 5.5" gap — the larger fish will view the smaller fish as food.
Score: 30.0/100 (GOOD ≥80, CAUTION ≥50, RISKY <50).
🔧 Tank Setup Requirements (for Both)
- Minimum tank: 30 gallons — sized for the larger fish in the pair.
- Temperature: keep it between 72°F and 74°F.
- pH: maintain 7.0 – 7.5.
- Hiding spots: essential for Goldfish — 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 30+ gallons:
Goldfish-specific flake food
Explore Related Checks
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Accuracy note: This tool uses expert rules + FishBase.org data. Individual fish behavior varies — a peaceful individual Goldfish 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.