Im going though kinda the same thing. Im setting up a 120g tank on my 1st floor, but have a basement. I currently have a 75g system, and the new 150g system will be on the other side of the same room for 2 weeks as it cycles. I heard something about anything over 100 or 150g(Cant remember) you have to resupport the floor. The new tank is going in the corner of 2 load bearing walls, so its probably ok. But just in case Im going to put up 2 new 4x4 supports and some 2x4 between beams.