Wow!! congrats on the 300gal score! I am currently setting up a 240gal reef tank and agree with the above comments. I am using a two tank sump system with a rubbermaid 70gal stock tank (to be filled with lr) and a custom 65g acrylic sump tank, set up in line. I put my tank on the first floor of my house, above a basement. It is positioned against a load-bearing wall that continues to the basement floor. In the basement this wall is concrete block. The tank sits perpendicular to the floor joists (crossing 5 of them). I also added two posts to support extra weight, each capable of holding 9000lbs. I figure my 240 system will weigh about 3500lbs complete, so I should be safe. Putting the tank on the first floor also allows for plumbing to the basement. This allows for my pumps, skimmer, heaters, and other equipment to stay downstairs, isolating the noise. Also, it makes water changes, and maintanance much easier. I can turn off the pumps, close a few valves, and drain my sump tank into a floor drain, for a water change. My wife is very happy that there is no mess in the family room. Good luck with everything!!