i dont think that this is a question that can SAFELY be answered via this forum. keep in mind a gallon of water weighs ~8.5#, plus your LR and sand, a robust stand, and (assuming you have one) a fuge and all it's water and rock, an ATO system/reservoir, etc. you are talking upwards of 1000# or more of very focused weight.
it all depends on the type of building, how it was built, type of materials used, tank placement on a load bearing beam or over an open span below, etc, etc etc.
as someone mentioned, you should definitely talk to an engineer or, at minimum, the management company.