Can Discus live with Red Tail Black Shark?
High risk due to water mismatch, aggression, or predation.
Why Discus and Red Tail Black Shark Don't Make an Easy Pair
There is no temperature overlap — Discus needs 82-86°F while Red Tail Black Shark needs 72-80°F. One of them will be outside its safe range constantly, which leads to chronic stress and disease. The size gap is 3.0" — Discus (8.0") and Red Tail Black Shark (5.0"). 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 |
Red Tail Black Shark
Epalzeorhynchos bicolor
| Adult Size: | 5.0" |
| Temperament: | semi-aggressive |
| Min Tank: | 30 gal |
| Temperature: | 72-80°F |
| pH Range: | 6.5-7.5 |
Water Parameter Overlap
| Parameter | Discus | Red Tail Black Shark | Overlap |
|---|---|---|---|
| Temperature | 82-86°F | 72-80°F | No overlap ✗ |
| pH | 6.0-7.0 | 6.5-7.5 | 0.5 ✓ |
Compatibility Breakdown
Temperament Match: peaceful + semi-aggressive. Semi-aggressive → watch territory and feeding.
⚠️ Size Predation Risk: Discus (8.0") vs Red Tail Black Shark (5.0"). A 3.0" 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: 0.0/100 (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 6.5 – 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.