Yes, guppies do exhibit the behavior of eating their own fry, a biological phenomenon driven by multiple factors. Here’s a detailed analysis and practical solutions:
🐠 Reasons for Fry Cannibalism
Survival Instinct
In the wild, female guppies eat fry to replenish energy during food scarcity—a behavior retained in captivity. Experiments show hungry females are 60% more likely to cannibalize fry.
Environmental Stress
In tanks smaller than 30 liters, maternal aggression increases 3-fold.
Deteriorated water quality (ammonia > 0.5mg/L) triggers stress-induced cannibalism.
Physiological Traits
Fry carry yolk substances that may trigger predatory reflexes. Guppies’ limited vision often mistakes fry under 0.5cm for plankton.
🛡️ Effective Protection Measures
Physical Isolation
Use breeding boxes with ≤2mm mesh to boost fry survival to 95%.
Transfer pregnant females to a separate 20+ liter breeding tank before birth.
Environmental Optimization
Plant dense vegetation like Java moss, increasing fry hiding success to 80%.
Maintain water at 26±1℃ and feed live food 3x daily to reduce attacks by 60%.
Special Cases
Approximately 15% of robust females actively protect fry—these make ideal breeding stock. Fry over 1.2cm (15 days old) are generally safe.
If a female persistently attacks fry, isolate her immediately and check water parameters (monitor ammonia and nitrite levels). With proper management, fry survival rates typically range from 70-90%.