Tink, I am using several layers of them in my Skippy. I built a frame out of (what else) PVC with lighting grid making two levels.
So there's maybe two layers of scrubber pads on the bottom level and 2-3 layers on the top level. The only ones I cut were the end ones to get them to fit around the incoming plumbing. They are not laying on the very bottom of the Skippy because that's where the water comes in and most of the gunk settles. They live forever and clean easily with either a pressure washer or one of those hose sprayer things. Loved the pressure washer to clean the Skippy, pads and grid.
Yes, only you can go to the dentist and come home with VERY EXPENSIVE pond equipment FOR FREE....I went to the dentist and came home with a list of very expensive dental repair that is to come.