I will ditto some of what has already been stated: find the load bearing wall, set the tank perpindicular to the floor joists, set it as close to the corner as possible, use a stand with a box type cponstruction so the weight is distributed evenly throughout. Make VERY certain the tank is leveled before filling. I would also use a sheet of rigid insulation between tank and stand to level out the smallest issues. I have had a 180g tank in 2 different places in my 2nd floor of a 110 year old house for about 10 years. No incidents. I do see some very mild bowing of the floor in the middle of the room this year, where the tank has been for about 5 years. I am going to move it shortly--it's making me nervous. You might want to research "shearing force" regarding floor integrity when you are gathering information. It's rather important. Good luck with your project. Getting renter's insurance was a wise idea. Plan ahead for spills and leaks as well as you can and make every effort to secure the integrity of the tank itself so you can sleep at night, LOL.
Best regards,
Harriett
** I use to dream of Unicorns ** NOW I dream of Discus with the colors of the Rainbow **