If you drive the O2 rates up through plant growth and good CO2, the surface films will go away.

I have identical tanks in terms of dosing, substrate plant biomass etc, when I varied the CO2 and reduced it, I got the surface film. I've repeated this on several tanks over of the years.

Better plant growth= less film.
These are for non surface skimmed tanks and with flourite, ADA AS, and Onyx sand.

With and without driftwood.

Regards,
Tom Barr