Diffused air mixing helps slow the eutrophication process of the pond and improves overall average water quality throughout the year.
Here are my comments from another thread that is very similar to your topic.
To all. Don't fall into the mental trap of thinking an aerator will solve overabundant algae issues. Firstly there are thousands of species of algae. Many with specific growth requirements that allows them to live in a wide variety of surface waters just about everywhere from your rain gutter, to snow banks & under ice, to thermal hot water springs of Yellowstone National Park.
Algae grows because there are excess nutrients that are not being consumed by some form of other plant. Thus the 'ever present everywhere' algae form massive growth parties 'slurping up' those available dissolved nutrients. 'Party hardy type guys'. I still continually look for scientific literature that tested and proves aeration reduces nutrients.
Don't get my meaning wrong. I love pond aerators and their ability to mix the entire water column and the many benefits that provides overall better water quality. Once you have a proper designed aerator system and see its benefits, you will not return it to the store for a refund. This activity overall improves water quality within the pond ecosystem. If aeration significantly reduced algae growth, I would have 20 aerators per acre in my pond.
Source was from this thread:
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Main=27398&Number=367975#Post367975
