Yes the back of the tank has some black tinting on the outside as far as I can tell. It's tough to see the back right now due to the lighting + cloudiness but it seems to be clearing up slowly.
Thanks; the Bifas are my favorite too. They look a lot better not in their breeding dress though in my opinion. Yes there are two different brands/sizes of PFS. I was given 350lbs of new PFS with the tank still in the bags. It's much nicer than my old sand. It's lighter in color, more rounded grains, and much larger grains. About 1/3 the size of a grain of dried rice. My old sand from the 180g is darker, smaller and a little more jagged. I anticipate in a month or two it will all be mixed together by the fish, but for now it's almost a 50/50 split. I still have 2 or 3 bags in the garage and will add them if needed.