cracked glass

Hello, So I just drilled my first glass tank. I'm pretty sure I did not break it after further investigation, but hopefully some internet confirmation will put me at ease for sure. So to start with the problem or what I thought was the problem is that I had the back painted with latex paint...

Just got my Red Sea Reefer 170. Set up the stand, then noticed my black background was scratched off a bit (was going to take it off anyway) and after I took it off, noticed two huge cracks in the overflow =( I checked the tank and sump before the driver left, but the overflow was so black and...