SS,

I've done larger water changes and cleaned up the tank as best as I can.
I also noted a correlation between sub optimal CO2 levels and pearling and SS layers.

Tanks with issues, sometimes for months where cleaned up fast when I added more plant biomass, increased the CO2 a little and optimalized things.

When plants are stressed due to CO2, they will release lipids and proteins that are hydrophobic. That's the scum. Foamy scum: lips/pro's+ fungi.

When plants really do well, less and the fungi being aerobic are easily able to handle the waste.

Regards,
Tom Barr