You can hide most anything with scaping.
Still, the scum is not a good sign of healthy planted tank IMO.
Something is causing an excess leakage of plant or bacterial lipids/proteins etc.
When there's plenty of O2, then the material is rapidly broken down..........
When O2 suffers, less than optimal plant growth/O2 etc then you get it.
I've added pure O2, it went away in several repeat test.
It'd come back when I stopped.
Later I noticed the CO2 was not up to snuff.
That corrected the appearance without O2.
I might have gone back and redid the same tank with cO2, but I did not.
Later, every time I've seen the scum, a water change and redoing the tweaking the CO2 resolved the issue along with some good water movement.
This did not isolate the cause/s, but it does show that it's O2 and perhaps plant growth(since O2 production is linked to plant growth).
Mild cases should clear up at night near the end of the light cycles and appear again early about the time the lights go on.
Plants also leak more scum/exudates etc when slightly stressed.
So it might be both the plant's leaking and the lower O2.
Not sure.
Regards,
Tom Barr