Structural engineers, architects, or general contractors can help you calculate the load. You could probably find a calculator online. Most residential homes are built to a 40 lb per sq ft spec. And most residential homes could support a piano, water bed and whatever else you want to put. For that tank i'd guess around 800 lbs. The longer the span in between walls underneath, and the closer to the middle of a given span will reduce the amount of weight you can put. With that weight, 800lbs, would say you can put it anywhere, as long as the span underneath isn't crazy long, like over 12-16 feet. With an aquarium it's not only a matter of can it support the weight, but how rigid it is. You don't want the water sloshing around when you walk past. Putting the tank up against the wall would be your best bet, if there's a wall directly below it even better.