IMO, I'm sure this happened after assembly, either at their plant or in shipping. It would be stupid to assemble a tank with a bad piece of acrylic, especially when you can use it on a slightly smaller tank after cutting it down. Plus, it's on a corner, so it would be reasonable to assume it happened from some type of light impact. I would definitely NOT immediately start filing anything to be hostile about it. The last thing you want to do is to piss off anybody you are looking for help from. I'm not saying never, but that should be the LAST thing to do once every amicable solution has been tried. Why can't you get a hold of anyone? Don't they answer the phone? How did you contact them to order? I would definitely make every attempt at a personal contact first, however you can do it. Good luck man. That sucks.