Can Harlequin Rasbora live with Lyretail Killifish?
These two species are usually compatible in community tanks.
Why Harlequin Rasbora and Lyretail Killifish Work
These two species overlap in both temperature (73–77°F overlap) and pH (6.0-7.0 overlap range). Their temperature tolerances are close enough, and neither fish pushes the pH so far outside the other's comfort zone that it creates chronic stress. The temperament match (peaceful + peaceful) is low-conflict. In a 10+ gallon tank with adequate hiding spots, these two can coexist with minimal problems.
Harlequin Rasbora
Trigonostigma heteromorpha
| Adult Size: | 2.0" |
| Temperament: | peaceful |
| Min Tank: | 10 gal |
| Temperature: | 73-79°F |
| pH Range: | 5.5-7.0 |
Lyretail Killifish
Aphyosemion australe
| Adult Size: | 2.5" |
| Temperament: | peaceful |
| Min Tank: | 10 gal |
| Temperature: | 72-77°F |
| pH Range: | 6.0-7.0 |
Water Parameter Overlap
| Parameter | Harlequin Rasbora | Lyretail Killifish | Overlap |
|---|---|---|---|
| Temperature | 73-79°F | 72-77°F | 4°F ✓ |
| pH | 5.5-7.0 | 6.0-7.0 | 1.0 ✓ |
Compatibility Breakdown
Temperament Match: peaceful + peaceful. Both peaceful → minimal conflict.
Score: 90.0/100 (GOOD ≥80, CAUTION ≥50, RISKY <50).
🔧 Tank Setup Requirements (for Both)
- Minimum tank: 10 gallons — sized for the larger fish in the pair.
- Temperature: keep it between 73°F and 77°F.
- pH: maintain 6.0 – 7.0.
- Hiding spots: essential for Harlequin Rasbora — 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 10+ gallons:
Plant supplement for planted tanks
Explore Related Checks
See what else works with these fish:
⚠️ Common Reasons This Pairing Fails in Practice
- Overcrowding: Even compatible species fail in tanks that are too small. Double the species means double the bioload — 25% weekly water changes are the minimum.
- Inadequate acclimation: Adding both species on the same day without quarantine is a common mistake. Always drip-acclimate new arrivals and quarantine for 2–4 weeks.
- Mismatched feeding: Harlequin Rasbora is a omnivore while Lyretail Killifish is a carnivore. Use targeted feeding zones and sinking vs. floating food to ensure both get proper nutrition.
Tools & Resources
Accuracy note: This tool uses expert rules + FishBase.org data. Individual fish behavior varies — a peaceful individual Harlequin Rasbora 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.