Compatibility Overview
Cardinal Tetra and Hillstream Loach can potentially coexist, but the combination requires careful attention. Some combination of water parameter differences, size mismatch, or temperament issues make this pair challenging. A larger tank (minimum 40 gallons), dense planting, and close monitoring are essential.
| Factor | Cardinal Tetra | Hillstream Loach | Verdict |
|---|---|---|---|
| Temperature | 73–82°F | 64–73°F | ⚠️ 73–73°F (narrow) |
| pH Range | 4.5–7.0 | 6.5–7.5 | ⚠️ 6.5–7.0 (narrow) |
| Temperament | peaceful | semi | ⚠️ Monitor |
| Adult Size | 1.5 in | 2.0 in | ✅ Similar |
| Min. Group | 6+ | 1+ | See below |
| Min. Tank Size | 40 gallons (for both species) | — | |
✅ Compatibility Positives
⚠️ Caution Points
Species Profiles
Cardinal Tetra — Paracheirodon axelrodi
Brilliant red-and-blue schooling fish from the Rio Negro. Prefers soft, acidic, warm water — a natural companion for discus.
→ Full Cardinal Tetra care guide
Hillstream Loach — Aquarium species
Sewellia lineolata, known as the Hillstream Loach, is a fascinating species for aquarists. These fish require a well-oxygenated, clear water environment with plenty of hiding spots. With a lifespan of 7 years, they are a long-term commitment. Their olive green color and slender body shape add a unique aesthetic to the tank. Despite their moderate activity le
Frequently Asked Questions
Can Cardinal Tetra live with Hillstream Loach?
With significant caution and a larger tank. Cardinal Tetra and Hillstream Loach can potentially coexist, but the combination requires careful attention. Some combination of water parameter differences, size mismatch, or temperament issues make this pair challenging. A larger tank (minimum 40 gallons), dense planting, and close monitoring are essential.
What tank size do I need for Cardinal Tetra and Hillstream Loach together?
A minimum of 40 gallons is recommended for keeping Cardinal Tetra and Hillstream Loach together. A larger tank improves water stability and reduces territorial conflict.
What temperature suits both Cardinal Tetra and Hillstream Loach?
73–73°F (narrow)
Is a Cardinal Tetra aggressive toward a Hillstream Loach?
Cardinal Tetra is peaceful and Hillstream Loach is semi. Their preferred temperature ranges have little or no safe overlap.
Related Compatibility Guides
Compatibility score breakdown
The overall score is weighted across water chemistry, behavior, adult size, swimming zone, and social needs. A score is a planning aid—not a guarantee for individual fish.
| Factor | Score |
|---|---|
| Temperature | 0/100 |
| Ph | 50/100 |
| Temperament | 75/100 |
| Adult Size | 100/100 |
| Swim Zone | 92/100 |
| Social Needs | 92/100 |
Tank size scenarios
Use the scenario that matches the actual group sizes and temperament you plan to keep.
| Scenario | Tank | When it applies |
|---|---|---|
| Minimum viable | 40 gal | Only for the recommended minimum groups, mature filtration, and close monitoring. |
| Recommended community | 55 gal | Adds territory, swimming room, and a safer buffer for behavior. |
| Low-conflict setup | 90 gal | Best when keeping larger schools or reducing territorial pressure. |