Separate fertility from infection
Opaque or white eggs may be unfertilized, damaged or colonized after death. Do not assume fungus was the original cause.
Check parent compatibility and maturity
Inexperienced pairs may miss fertilization, eat eggs or abandon a clutch. Chronic aggression can also prevent successful spawning.
Review water and oxygen
Temperature swings, ammonia, nitrite, poor circulation and abrupt chemistry changes can affect eggs and larvae.
Audit first food timing
A hatch can look successful until fry exhaust the yolk sac and fail to find food small enough to eat.
Consider genetics and stock health
Repeated deformities, weak growth or poor fertility may indicate relatedness, inherited problems or unhealthy breeding stock. Stop and seek qualified advice.