I am new to this hobby. I just setup a new 45 gal
freshwater aquarium 3 weeks ago. It sits on a wood stand on a carpet. It is slightly unleveled. It is about 1/4 inch at the right end corner on the back side and about 1/8 on the front corner. I think it is ok. If I add about 1/2 gallon of water, you cannot notice the unevenness. But because I am new to this, I like to get advice from more experienced aquarists.