After looking at your pics I see the algae your are talking about. Once temps drop this fall it will disappear. Is your diffuser in the center of the pond? If it was, all that floating algae would be pushed to the shoreline and probably dissapate. Of course I would make changes before winter sets in. Have you tried augmenting with bacteria? I would still stay away from the algaecide unless absolutely necessary.

Any idea where the nutrients are coming from? Do you fertilize your yard? Did you before you dug the pond?

Another possibility is your diffuser in churning up the bottom and putting nutrients into the water column. Is it about a foot off the bottom or do you have a good underlayment under it? Could it be oversized for the pond size?

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.