Planktonic Algae is important because it's what feeds the zooplankton which feeds the lower end of the food chain (minnows, YoY fry). Planktonic Algae is a sign of a very fertile pond, albeit aesthetically unappealing.
From
https://extension.psu.edu/planktonic-algae ....
-Planktonic algae are at the base of the food chain in the pond or lake.
-They are fed on by zooplankton (microscopic animals) which, in turn, become food for fish.
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Ponds with abundant planktonic algae are often able to support larger populations of fish that grow more quickly.-Excessive growth of planktonic algae will cloud the water, making it less aesthetically pleasing.
-Overabundance of planktonic algae can lead to fish kills in the late summer and fall. This occurs when the large number of algae dies suddenly due to colder air temperatures.
Prevention
After reading that site, I'd say prevention is your best option, rather than chemicals every year. The oak leaves are definitely contributing to the fertile water. Do you have vegetation around the edges of your pond to absorb any of the nutrients? That might be an option too.
