We thought of using pond liner as well. Our concern about it was that full grown wtf's LOVE to redecorate and were worried that one might manage to dig under the liner and possible mess up the entire flow of the water. One of our previous wtf's (I blamed Pumba since he was always in the water) managed to move some pretty large rocks and block the water in their tank from the water pump. I had to replace the pump. The fact that I am a plumbing designer and using 2" pvc just tickles me pink in a weird demented way. My boss would be proud.

I figured we would try the pvc and if it didn't work the way I want during trial runs (And there WILL be trial runs), I will run out and pick up some liner. Maybe even just lay some liner over the pvc? Overkill?