White stuff on surface of water during cycling?

[cf21]

I found some white film on the surface of my jar. Is it sale from evaporation or maybe limescale? Or do I finally have biofilm? Currently only have macroalgae chaeto in there. Receives room light and sometimes direct sunlight by the window if weather is good.

[KiwiCordell]

I think it’s biofilm, can you use a net to remove it?

[cf21]

Yes. I decided to leave it in there for now

[Mustafa]

Yep, probably biofilm. Harmless, potential food for the shrimp.