Weird flaky? stuff on surface of water

[lexoZGB]

I have a 60L aquarium which I set up a week ago. I put water conditioner in and let it be with the filter running for 24hrs. On Wednesday I wanted to put easystart bacteria but I saw that there were some weird things floating on the surface (on the pictures). After doing some research later, I found out that it's called surface scum and that it can be removed by placing a kitchen paper on the surface, and that actually helped remove almost all of it. Well after thinking for a bit I don't think it is "surface scum", because to my knowledge surface scum is oily and made from bacteria/algae and I have no real plants (or fish) and just started preparing the aquarium. Anyway, a day or two later and this stuff began appearing again. What I suspect is that the tap water I used for the aquarium is too hard and the stuff floating on the surface are some sort of minerals or "limescale", if that's the correct term (not a native speaker).
(or maybe these are just dust particles that have settled on the gravel while the aquarium was waiting for the water filling and I'm just overreacting)

I'd really appreciate some help and solutions to this problem, or if anyone can clear up what that stuff actually is.

 

[Caliban07]

Not sure to be honest. Could be dust as you say or a mineral precipitate but I’ve never seen the latter to this degree.

Try removing it and do another water change.

 

[Mpwallace1]

You said you just set up this 60 gallon recently. Is the media in your filter brand new and did you rinse it 1st?

 

[Aiken Drum]

You said you just set up this 60 gallon recently. Is the media in your filter brand new and did you rinse it 1st?

Good call. That looks just like the residue that came off some of my filter media (fluval biomax) when i cleaned it.