Short Answer:
A healthy pond should have 5–8 mg/L of dissolved oxygen, with at least 3 mg/L minimum.
Detailed Answer:
- 5–8 mg/L → Ideal for fish and aerobic bacteria
- 3–5 mg/L → Stressful for fish
- Below 3 mg/L → Risk of fish kills
When oxygen drops:
- Hot summer nights
- Cloudy days (less photosynthesis)
- After algae die-offs
Best prevention:
Consistent aeration, especially overnight during warm weather.
