From my past bad experiences, I would never use anything but a true Firestone 45 mil liner (or thicker). I have used the cheaper PVC liners sold at Lowe's and it was very frustrating when they leaked. they tear VERY easily. I went through two of these and finally learned a lesson that they are garbage. The last one I installed in the spring last year and a couple of branches made some serious holes in it during the early winter. That thing didn't even last a year! After getting the Firestone liner, I couldn't believe how much thicker and stretchable it was compared to the PVC. There was absolutely no comparison! I doubt they would have suffered the same damage as the PVC. I don't think they would have even been affected. I also used the official underlayment this time. I wasn't going to fool around this time. My pond is 1500 gallons with 28 fish. So, it's a big hassle to change the liner. I also have tons of rocks surrounding it with a bunch of large rocks for the waterfall.