45 mil pond liner is pretty thick material. It takes ALOT to puncture that. I'm not saying it can't happen, but ... it's not uncommon to see salesman stab a section of 45 mil pond liner with a pair of scissors and not puncture it. Like I said it really does take alot.
I have set up several pods for people over the years mostly outdoor, never had one of mine leak from a puncture, but I have seen a couple leak from a puncture. One was from a tree falling on it.
Some guys keep rays in cheap pop up swimming pools. Those are not even 45 mil lol.
When I set my indoor pond up I will be using a piece of 45 mil I have laying around. Will just keep the folds to a minimum. You could always mount a structure in the corners to keep the rays away from the folds. Just an idea.