The skimmer sounds a bit daunting to me. I’ll be honest, I was hoping for a bit “easier” solution.
Agreed. I was hoping someone else would chime in with an easier solution.
I don't even know if you can skim enough water to make a difference. However, if you already own any type of water pump, you could start the experiment.
Put a 5-gallon bucket in a flat, sandy spot of your pond. Work it down in the sand so that the rim of the bucket is 3/4 of an inch below the water surface. Put the suction hose of your pump in the bottom of the bucket. Put the discharge hose over the dam (if you have plenty of water supply), or as far away as possible back into your pond.
Just observe if you can draw a significant amount of pond scum into the bucket on a windless day.
If that works, then you can optimize the depth of the bucket rim beneath the surface.
Then you may be able to just build a box for your skimmer. Instead of complicated screens to filter out the scum particulate matter, you could just discharge the "pond scum" water over the dam for two days when you are fairly certain you have rain in the forecast.
I am also a big fan of hybrid systems. If the skimmer only works a little bit, you could try pool noodles on a rope and mechanically skim the pond and then draw the rope into a circle around the skimmer. Maybe the skimmer efficiency would greatly improve if it was processing concentrated pond scum!
Azteca's ideas for biological solutions are even better - if you can find something that targets your particular pond scum.
