Hi! I was wondering what are the exact dimensions of a 75 gallon tank. Is it 48 x 18 or 48 1/2 x 18 1/2? The reason is I bought this stand from a guy and it is 48 1/2 x 18, closed on the front and side by some wood but open on the back. So if it is 18 1/2 there would be half an inch that would come out from the stand. Would that be significant at all? Thanks!!!