I have been investigating Solar aeration systems. From what I have read a lot of people recommend running aeration 24/7 or overnight. The systems I looked at don't have batteries so I don't see how this is possible. The pond is in the Deep South so not used to keep ice off the pond. Thanks in advance for any help

Plants,phytoplankton and algae make oxygen during periods of sunlight as a part of photosynthesis, but during times of low or no sunlight they use oxygen. In nutrient rich ponds where there is a lot of phytoplankton, algae, fish and plants in a pond, the oxygen levels can drop low enough during the nighttime hours to kill fish.

So Esshup, another silly question. If you were going to run aeration for only a few hours per day each day then it seems the best time to run it would be at night right?

Correct. If only for a few hours during the summer or when the pond is not frozen, I would pick the "few" hours before sunup. That's when the O2 levels are the lowest.

During the winter, if there's ice and 2"+ (yes, inches) of snow on the pond, then I would consider running during the day. The diffuser will create open water, allowing both sunlight to help any phytoplankton produce O2 and the water to absorb O2 from the air. If the ice is clear, and no snow on it, then I'd consider running it at night during the winter. But, how often is the ice clear with no snow cover?

FWIW I am currently running mine between 2 and 4 AM. I will increase the run time as the water gets warmer.

So can you run a system enough during the day to insure that you don't have problems during nighttime hours. If the answer is no, then what good is a solar powered system without battery storage?

That's a question that I can't answer. I think that is a very good question too!