Okay, please put my worries to rest. Is it even possible for a ray to bite through a pond liner (typical black firestone variety)? I tried, and it is damn hard, but I have one MM that likes to chew on things such as my so sponge filters! You see I was not able to fold the pond in perfectly on the bottom, there are some creases on the floor that are near impossible to smooth out, they are from the way the pond was folded in the box.