Can Hillstream Loach live with Silver Arowana?
High risk due to water mismatch, aggression, or predation.
Why Hillstream Loach and Silver Arowana Don't Make an Easy Pair
There is no temperature overlap — Hillstream Loach needs 64-75°F while Silver Arowana needs 75-82°F. One of them will be outside its safe range constantly, which leads to chronic stress and disease. The size gap is 33.5" — Hillstream Loach (2.5") and Silver Arowana (36.0"). A fish that fits in another fish's mouth will eventually end up there.
Hillstream Loach
Sewellia lineolata
| Adult Size: | 2.5" |
| Temperament: | peaceful |
| Min Tank: | 20 gal |
| Temperature: | 64-75°F |
| pH Range: | 6.5-7.5 |
Silver Arowana
Osteoglossum bicirrhosum
| Adult Size: | 36.0" |
| Temperament: | semi-aggressive |
| Min Tank: | 250 gal |
| Temperature: | 75-82°F |
| pH Range: | 6.0-7.5 |
Water Parameter Overlap
| Parameter | Hillstream Loach | Silver Arowana | Overlap |
|---|---|---|---|
| Temperature | 64-75°F | 75-82°F | No overlap ✗ |
| pH | 6.5-7.5 | 6.0-7.5 | 1.0 ✓ |
Compatibility Breakdown
Temperament Match: peaceful + semi-aggressive. Semi-aggressive → watch territory and feeding.
⚠️ Size Predation Risk: Hillstream Loach (2.5") vs Silver Arowana (36.0"). A 33.5" 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: 10.0/100 (GOOD ≥80, CAUTION ≥50, RISKY <50).
🔧 Tank Setup Requirements (for Both)
- Minimum tank: 250 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 – 7.5.
- Hiding spots: essential for Hillstream Loach — 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 250+ gallons:
Floating food sticks for large carnivorous surface feeders
Explore Related Checks
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Accuracy note: This tool uses expert rules + FishBase.org data. Individual fish behavior varies — a peaceful individual Hillstream Loach 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.