if you can, email me the what size of floor joists, what the spacing is on the floor joists, what is the span of the floor joists and where is the tank set up in relation to the supports of the floor joists. my husband is a liscensed builder and can do a structural analysis for you. roughly guessing you are going to have to support 1500 lbs for the tank and water. you will want to make sure that the tank is level throughout the set up and after. a peice of styrofoam about an inch thick will act like a shock absorber for the tank, giving it some give so as not to become unlevel. unlevel tanks can twist and eventually break. not the most fun to clean up after. take my word for it!
maggie