Can Harlequin Rasbora live with Rainbow Shark?
Case-by-case. Watch group sizes, tank size, and feeding zones.
Why Harlequin Rasbora and Rainbow Shark Don't Make an Easy Pair
They can coexist, but you need to manage the setup carefully. The temperament combination (peaceful+semi-aggressive) can work, but you will need to watch them at feeding time for the first week.
Harlequin Rasbora
Trigonostigma heteromorpha
| Adult Size: | 2.0" |
| Temperament: | peaceful |
| Min Tank: | 10 gal |
| Temperature: | 73-79°F |
| pH Range: | 5.5-7.0 |
Rainbow Shark
Epalzeorhynchos frenatum
| Adult Size: | 6.0" |
| Temperament: | semi-aggressive |
| Min Tank: | 55 gal |
| Temperature: | 72-82°F |
| pH Range: | 6.5-7.5 |
Water Parameter Overlap
| Parameter | Harlequin Rasbora | Rainbow Shark | Overlap |
|---|---|---|---|
| Temperature | 73-79°F | 72-82°F | 6°F ✓ |
| pH | 5.5-7.0 | 6.5-7.5 | 0.5 ✓ |
Compatibility Breakdown
Temperament Match: peaceful + semi-aggressive. Semi-aggressive → watch territory and feeding.
⚠️ Size Predation Risk: Harlequin Rasbora (2.0") vs Rainbow Shark (6.0"). A 4.0" gap — the larger fish will view the smaller fish as food.
Score: 60.0/100 (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 73°F and 79°F.
- pH: maintain 6.5 – 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 55+ gallons:
High-quality freshwater flake food
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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.