Can Bristlenose Pleco live with Lyretail Killifish?
Case-by-case. Watch group sizes, tank size, and feeding zones.
Why Bristlenose Pleco and Lyretail Killifish 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.
Bristlenose Pleco
Ancistrus cirrhosus
| Adult Size: | 5.0" |
| Temperament: | peaceful |
| Min Tank: | 20 gal |
| Temperature: | 72-82°F |
| pH Range: | 6.5-7.5 |
Lyretail Killifish
Aphyosemion australe
| Adult Size: | 2.5" |
| Temperament: | peaceful |
| Min Tank: | 10 gal |
| Temperature: | 72-77°F |
| pH Range: | 6.0-7.0 |
Water Parameter Overlap
| Parameter | Bristlenose Pleco | Lyretail Killifish | Overlap |
|---|---|---|---|
| Temperature | 72-82°F | 72-77°F | 5°F ✓ |
| pH | 6.5-7.5 | 6.0-7.0 | 0.5 ✓ |
Compatibility Breakdown
Temperament Match: peaceful + peaceful. Both peaceful → minimal conflict.
⚠️ Size Predation Risk: Bristlenose Pleco (5.0") vs Lyretail Killifish (2.5"). A 2.5" 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: 60.0/100 (GOOD ≥80, CAUTION ≥50, RISKY <50).
🔧 Tank Setup Requirements (for Both)
- Minimum tank: 20 gallons — sized for the larger fish in the pair.
- Temperature: keep it between 72°F and 77°F.
- pH: maintain 6.5 – 7.0.
- Hiding spots: essential for Bristlenose Pleco — 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 20+ gallons:
Sinking algae rounds for plecos and herbivores
Explore Related Checks
See what else works with these fish:
⚠️ Common Reasons This Pairing Fails in Practice
- Size-based predation: The 2.5" 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.
- Diet-driven aggression: A carnivore sharing a tank with bite-sized tank mates creates structural risk — no amount of generous feeding eliminates the instinct to hunt.
- 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.
- Mismatched feeding: Bristlenose Pleco is a herbivore while Lyretail Killifish is a carnivore. Use targeted feeding zones and sinking vs. floating food to ensure both get proper nutrition.
Tools & Resources
Accuracy note: This tool uses expert rules + FishBase.org data. Individual fish behavior varies — a peaceful individual Bristlenose Pleco 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.