Chalky, white substance on glass

[Cakes]

I am not sure how to remove it. I used a ph lower powder a couple weeks ago that seems to have coated my tank with a slight powder like film. My standard method of scrubbing isn't working, either is my kent marine pro scraper. When I use just my fingers it slowly works, but on my 180G it would take a couple hours. It seems with reg scrubbing the film seems to be trapped between the pad and glass and gets rubbed back in.

Any thoughts, what is your preferred method?

Thanks in advance.

BC