Can Discus live with Harlequin Rasbora?
High risk due to water mismatch, aggression, or predation.
Why Discus and Harlequin Rasbora Don't Make an Easy Pair
There is no temperature overlap — Discus needs 82-86°F while Harlequin Rasbora needs 73-79°F. One of them will be outside its safe range constantly, which leads to chronic stress and disease. The size gap is 6.0" — Discus (8.0") and Harlequin Rasbora (2.0"). A fish that fits in another fish's mouth will eventually end up there.
Discus
Symphysodon aequifasciatus
| Adult Size: | 8.0" |
| Temperament: | peaceful |
| Min Tank: | 55 gal |
| Temperature: | 82-86°F |
| pH Range: | 6.0-7.0 |
Harlequin Rasbora
Trigonostigma heteromorpha
| Adult Size: | 2.0" |
| Temperament: | peaceful |
| Min Tank: | 10 gal |
| Temperature: | 73-79°F |
| pH Range: | 5.5-7.0 |
Water Parameter Overlap
| Parameter | Discus | Harlequin Rasbora | Overlap |
|---|---|---|---|
| Temperature | 82-86°F | 73-79°F | No overlap ✗ |
| pH | 6.0-7.0 | 5.5-7.0 | 1.0 ✓ |
Compatibility Breakdown
Temperament Match: peaceful + peaceful. Both peaceful → minimal conflict.
⚠️ Size Predation Risk: Discus (8.0") vs Harlequin Rasbora (2.0"). A 6.0" 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: 20.0/100 (GOOD ≥80, CAUTION ≥50, RISKY <50).
🔧 Tank Setup Requirements (for Both)
- Minimum tank: 55 gallons — sized for the larger fish in the pair.
- Temperature: no safe overlap range exists. A heater is not enough to fix this pairing.
- pH: maintain 6.0 – 7.0.
- Hiding spots: essential for Discus — 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:
Premium canister filter for discus tanks
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Accuracy note: This tool uses expert rules + FishBase.org data. Individual fish behavior varies — a peaceful individual Discus 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.