falling through my floor?

[Darth Wader]

I have a 95 gallon tank in my living room and I'm on the second floor in a super old building and I'm running parallel to the floor joists but i'm clost to 2 load bearing walls. Like Fkshiu said it really depends on tank placement. If you have 2x6 or 2x8 joists and you run perpendicular you shouldnt have a problem. And if you can position it next to a load bearing wall you're pretty much good to go. Having hardwood like most older places do helps, thats a good way to spread the load.
I wouldnt worry to much, however having said that I alsmost sh!t my pants when the floor started creaking as I was filling up my tank, (good thing I got renters insurance that week).