I will go 6 hours a day (just to be safe) from now on with my 1/4. Is there a "best" time of day to run? I've read that lowest DO occurs at night, so would Midnight to 6 AM be a good choice for run time?
Ponds are complex dynamic always hourly changing ecosystems similar to the human body. Stuff is always happening even during sleep (dark) periods. There are all sorts of recommendations for length of partial run times for aerators and when to run the aerator. Some advocate to operate a few hours twice a day. There are pros and cons of each opinion. One of the main things for aerator run time length is how much 'overkill' or extra mixing potential that you have built into your aerator system. For many package or custom designed systems, the system is designed to be just adequate or it is even under sized (mostly in bigger ponds) and thus it needs to run 24/7 to get the proper number of pond water turnovers per day. Generally you want a minimum of one turnover per day. If in a smaller pond, I can get that turnover in 2 to 4 hrs, then running the aerator 6 hrs/day provides very adequate turnover - pond mixing of 2 maybe 3 turnovers. I specialize in smaller pond management 1 ac or less.
For most 'normal' ponds with adequate or extra mixing potential it does not make much difference when you run the aerator. However, if you are trying to run the aerator less per day and your system is just adequate and not oversized, then night or very early morning (2-4am) or pre-daylight mixing is best. This is because the DO starts to get consumed after dark and DO loss continues or progresses toward daylight. Mixing and reoxygenating late night before the DO drops too low is best. Thus nightly running the aerator is a good time to operate it on a limited basis. I often suggest when nightly running that aerator to have it shut off after you get up so you can verify that it did run that night.
At daylight sunlight stimulates DO production by the planktonic algae, benthic algae, and other underwater plant life. DO continues to build or increase during the day with maximum daily DO usually near sunset. Several of the factors that influence the DO production are temperature, water clarity, condition of the bloom, predominant type of plant life, and brightness of the sun vs a cloudy and or rainy day and pond dye. Pond dye inhibits the ability of aquatic plants to produce DO. A dying plant bloom at night is consuming (respiration) more DO per minute than a healthy plankton bloom. This is because the bacteria decomposing the dying plankton has more respiration (DO consumption) that just regular night respiring algae. Plus the dying bloom will not make as much DO in daylight as a healthy or growing bloom. FYI the algae (plants) also use DO during the day (respiration), however they usually (sunshine) make excess DO that then dissolves into the water increasing the DO.
