Ya I'm with that problem. Figure a 300 gallon tank is gonna weigh somewhere around 3000 pounds. I am not gonna put that anywhere in my house, except where I have slab on grade. Most people can do this in there basement, my basement has a wood subfloor just like the rest of the house(I actually have a 30" crawl space under my basement. So what I am doing is extending my office into my garage were I will be able to place my 300g or 370g tank on a concrete slab and a foundation wall. I'm hoping for this to happen by the end of summer.
Here's a pic of my 120g tank,