Can Hillstream Loach live with Yellow Tang?
High risk due to water mismatch, aggression, or predation.
Why Hillstream Loach and Yellow Tang Don't Make an Easy Pair
There is no temperature overlap — Hillstream Loach needs 64-75°F while Yellow Tang needs 75-80°F. One of them will be outside its safe range constantly, which leads to chronic stress and disease. The size gap is 4.5" — Hillstream Loach (2.5") and Yellow Tang (7.0"). 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 |
Yellow Tang
Zebrasoma flavescens
| Adult Size: | 7.0" |
| Temperament: | semi-aggressive |
| Min Tank: | 75 gal |
| Temperature: | 75-80°F |
| pH Range: | 8.1-8.4 |
Water Parameter Overlap
| Parameter | Hillstream Loach | Yellow Tang | Overlap |
|---|---|---|---|
| Temperature | 64-75°F | 75-80°F | No overlap ✗ |
| pH | 6.5-7.5 | 8.1-8.4 | No overlap ✗ |
Compatibility Breakdown
Temperament Match: peaceful + semi-aggressive. Semi-aggressive → watch territory and feeding.
⚠️ Size Predation Risk: Hillstream Loach (2.5") vs Yellow Tang (7.0"). A 4.5" gap — the larger fish will view the smaller fish as food.
Score: -10/100 (GOOD ≥80, CAUTION ≥50, RISKY <50).
🔧 Tank Setup Requirements (for Both)
- Minimum tank: 75 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: no shared range. One species will be outside its tolerance regardless of what you set.
- 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 75+ gallons:
Dried seaweed sheets for marine herbivores
Explore Related Checks
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⚠️ Common Reasons This Pairing Fails in Practice
- Zero temperature overlap: No heater setting can satisfy both species. One will be chronically stressed, leading to disease susceptibility.
- Size-based predation: The 4.5" size gap means the larger fish may eat the smaller one once it grows to full size. This is not fixable with more hiding spots.
- 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.
Tools & Resources
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.