Medaka Hatching Time
Estimated Medaka Egg Hatching Time by Water Temperature
The table below shows estimated medaka egg hatching time based on the Degree-Day (DD) model, assuming a developmental threshold of 50°F and an average requirement of 270 DD°F.
| Water Temperature (°F) | Daily Degree-Days (DD/day) | Estimated Days to Hatch |
|---|---|---|
| 68°F | 18 | ~15.0 days |
| 70°F | 20 | ~13.5 days |
| 72°F | 22 | ~12.3 days |
| 75°F | 25 | ~10.8 days |
| 77°F | 27 | ~10.0 days |
| 78.8°F | 28.8 | ~9.4 days |
| 80°F | 30 | ~9.0 days |
| 82°F | 32 | ~8.4 days |
Degree-Day (DD) Formula
Medaka egg development progresses only above a minimum threshold temperature. The Degree-Day model calculates effective heat accumulation over time.
Formula (Fahrenheit)
DD = (Water Temperature °F − 50°F) × Days
- Threshold temperature: ~50°F (10°C)
- Required DD for hatching: ~252–288 DD°F (≈270 DD°F average)
For example, at an average water temperature of 78.8°F:
- Daily DD = 78.8 − 50 = 28.8 DD/day
- Days to hatch = 270 ÷ 28.8 ≈ 9.4 days
While higher temperatures reduce hatching time, maintaining a stable environment is more important than accelerating development. For most setups, 75–80°F provides the best balance between speed and fry health.
