Several years ago I got fed up with the duckweed in the pond and saw a video of something in america that was made to get rid of surface rubbish. I thought I could make one and its been in for several years doing a good job, it's a bit of a wobbly video but here's a clip of me cleaning it out
I used two 3d printed parts and ordinary sink waste pipe as well as a bit of stainless steel mesh. 3D files scumskimmer5.blend skimmerinsert1.blend scumskimmer5.stl skimmerinsert1.stl
a rough diagram showing filter head and pipe