I just bought a used 20 Long tank for my mother's birthday. It didn't come with a lid or light so i went to the LPS and bought a versa hood for it. I brought it home and it doesn't fit!!!!! The lid is for a 20 long and i know this tank is a 20 long. The owner of the pet store said that it must be an old tank and there is nothing i can do. Do you guys have any suggestions so that the lid and light don't sit lop sided ontop of the tank????