I cut down when i saw you said i might be overfeeding and the foam is decreasing. So again i bow to your superior knowledge! Just checking that the foam wouldn't be a problem for fish, all other readings show water is excellent quality. Thanks.
Skasmo, I cleaned my filter and added some enzymes last night, and few hours after topping off this morning, my pond looked much like your picture. My first thought was the enzymes or something in the city water. But when I opened up the skimmer to scoop out the foam that sometimes collects on either side of the leaf basket, there was none.
Though the foam looked threateningly unfamiliar, it was just normal foam from pollen and whatnot. But my overflow had shifted slightly, allowing the the water to rise just above the skimmer weir. Hence, the skimmer stopped skimming the surface, allowing the foam to build up, and a small amount of foam that would normally go unnoticed appeared to be a major new problem.
I'm not sure if this is relevant to your situation, but my foam looked exactly like the stuff floating on your pond.
I just checked on the pond again, and not only is the surface clear now, there is only the slightest trace of foam in the skimmer, just a few transparent bubbles. The currents in the skimmer must have put the foam back into solution. There are no bubbles drifting across the pond from the waterfall either. The bubbles dissipate within about a foot, and after that, it's just clear water.
Hence I wonder if you weren't overfeeding after all. Maybe you or rain overfilled your pond. And as the water level dropped from evaporation, and skimmer started drawing from the surface again, the foam went back into solution.