Fear of falling through floor! Real or Not?

[Doormatt]

Be worried.

Bathtubs are placed over additional support when built, so they can easily take the 400-600 pounds of weight. From what I've read, the limit for "anywhere" placement is a 55 gallon tank. Anything above that needs to be either placed against a retaining wall, or have additional support added. Personally, I'd call in a structural engineer if I was going to put a 180 gallon tank on a non-main floor.