Can Cardinal Tetra live with Lawnmower Blenny?
Case-by-case. Watch group sizes, tank size, and feeding zones.
Why Cardinal Tetra and Lawnmower Blenny Don't Make an Easy Pair
They can coexist, but you need to manage the setup carefully. The temperament combination (peaceful+peaceful) can work, but you will need to watch them at feeding time for the first week.
Cardinal Tetra
Paracheirodon axelrodi
| Adult Size: | 1.5" |
| Temperament: | peaceful |
| Min Tank: | 10 gal |
| Temperature: | 73-81°F |
| pH Range: | 5.0-7.0 |
Lawnmower Blenny
Salarias fasciatus
| Adult Size: | 5.0" |
| Temperament: | peaceful |
| Min Tank: | 30 gal |
| Temperature: | 74-82°F |
| pH Range: | 8.1-8.4 |
Water Parameter Overlap
| Parameter | Cardinal Tetra | Lawnmower Blenny | Overlap |
|---|---|---|---|
| Temperature | 73-81°F | 74-82°F | 7°F ✓ |
| pH | 5.0-7.0 | 8.1-8.4 | No overlap ✗ |
Compatibility Breakdown
Temperament Match: peaceful + peaceful. Both peaceful → minimal conflict.
⚠️ Size Predation Risk: Cardinal Tetra (1.5") vs Lawnmower Blenny (5.0"). A 3.5" gap — the larger fish will view the smaller fish as food.
Score: 70/100 (GOOD ≥80, CAUTION ≥50, RISKY <50).
🔧 Tank Setup Requirements (for Both)
- Minimum tank: 30 gallons — sized for the larger fish in the pair.
- Temperature: keep it between 74°F and 81°F.
- pH: no shared range. One species will be outside its tolerance regardless of what you set.
- Hiding spots: essential for Cardinal Tetra — 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 30+ gallons:
Dried seaweed sheets for marine herbivores
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Accuracy note: This tool uses expert rules + FishBase.org data. Individual fish behavior varies — a peaceful individual Cardinal Tetra 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.