Can Jack Dempsey live with Swordtail?
Case-by-case. Watch group sizes, tank size, and feeding zones.
Why Jack Dempsey and Swordtail Don't Make an Easy Pair
They can coexist, but you need to manage the setup carefully. The temperament combination (aggressive+semi-aggressive) can work, but you will need to watch them at feeding time for the first week.
Jack Dempsey
Rocio octofasciata
| Adult Size: | 10.0" |
| Temperament: | aggressive |
| Min Tank: | 55 gal |
| Temperature: | 72-82°F |
| pH Range: | 6.5-8.0 |
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 | Jack Dempsey | Swordtail | Overlap |
|---|---|---|---|
| Temperature | 72-82°F | 72-78°F | 6°F ✓ |
| pH | 6.5-8.0 | 7.0-8.0 | 1.0 ✓ |
Compatibility Breakdown
Temperament Match: aggressive + semi-aggressive. One aggressive → predation/nipping risk.
⚠️ Size Predation Risk: Jack Dempsey (10.0") vs Swordtail (5.0"). A 5.0" gap — the larger fish will view the smaller fish as food.
⚠️ Diet Conflict: A carnivore sharing water with a fish small enough to fit in its mouth is a waiting game. Feed generously, but the risk is structural — not something you can manage meal by meal.
Score: 55.0/100 (GOOD ≥80, CAUTION ≥50, RISKY <50).
🔧 Tank Setup Requirements (for Both)
- Minimum tank: 55 gallons — sized for the larger fish in the pair.
- Temperature: keep it between 72°F and 78°F.
- pH: maintain 7.0 – 8.0.
- Hiding spots: essential for Swordtail — 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 55+ gallons:
Floating pellet for medium to large cichlids
Explore Related Checks
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Accuracy note: This tool uses expert rules + FishBase.org data. Individual fish behavior varies — a aggressive individual Jack Dempsey 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.