Are there any other limitations (such as the weight that the floor can handle) that would come into play?
and there are more than petco and pet supplies plus that run good sales on aquariums.
From memory, That Pet Place in Lancaster PA will have $1/gallon sales on larger tanks, at their customer appreciation and anniversary sales. I'm not 100% sure, but I think 75, 90 and 125g tanks are included also.