I'm not seeing any cyano
in those picks, it does look like a dusting of diatoms.
Well, maybe those light pink spots, but it could also be coralline. If it grows fast and if it looks like a "sheet", than cyano
. If it looks like dust, diatoms.
you should go ahead and do about a 75% water change then research which of the fish you want to get is the hardiest and start adding livestock.
Not to sure about the idea of adding snails and such this early, there is nothing for them to graze on so you will have to be concerned about specifically feeding them and that will impact the water quality negatively. You should wait at least 1-2 months after adding your desired fish stock before adding any critters classified as "clean-up crew".
I learned that the hard way.