In general cooler water and moving water have better oxygen levels, I would leave the culvert area alone.
Day 1: 15 min
Day 2: 30 min
Day 3: 60 min
Day 4: 2 hours
Day 5: 4 hours
Day 6: 8 hours
Day 7: 16 hours (or 12 hours)
Day 8: 24 hours
I like to run my aeration time from 8PM until 8AM, the lowest O2 levels usually occur just before sunrise. In the heat of the summer I watch the weather forecasts for strong cold fronts, once they get here I will run aeration 24/7 until the weather stabilizes and the sun comes back out. Three solid days of cold, rainy, calm and overcast conditions can trigger an algea bloom die off and dissolved oxygen crash which can be the cause a summer fish kill.
