I have a 125 and 75 on my main floor that is on top of a finished basement. I added a steel supporting pole in my basement to support the 125 which runs along a girder, and nothing for the 75 which runs across the girders. I don't worry about weight but paranoid about 200 gal flooding my hardwood floor. My tanks are new and I don't trust used tanks. Also, I use only simple HOBs and don't trust canister or sump system with external plumbing that is vulnerable to leak.
I used to have all my tanks in my basement which I don't worry about weight or flooding. But what's the point of hiding myself and show tanks in the basement no visitors can appreciate.