My bottom is just regular, filtered pool sand. I can't seem to wrap my head around it either? So weird. I do have an email into the manufacturer and the pool store. I will update this thread if/when I receive an answer.
Oh yeah. already on it with them. Not really excited to think of replacing the liner already. Since I know they will only pay for the liner and not the install and replacement water.
Casey, we have the same liner. You should see how faded the bottom of mine is. Some places there is no color at all. Its where I would sprinkle the shock weekly before coming here and the low circulation area after my steps is real white. I think because the water is so clear there is noting filtering the suns rays. My best guess is the Pool Store way always had some algea floating around to help filter the rays. Still holds water and that's all that counts.