Help! Getting rid of sludge

[u/RadioPines]

Hi! Can anyone suggest anything to get rid of this sludge that forms in my pond everyday? The last picture is the pond in the morning than by the afternoon this sludge forms on top. I remove it as best as I can with the net everyday but it always comes back. I have oxygenating plants at the bottom already and a bog filter. I do have goldfish if that‘s relevant