55 gallon aquarium on the 3rd floor.

It's a full size appt, not an attic.

 

Justvthinking outloud here, wouldn't a full grown man put the same force over one square foot as a 55 gallon aquarium?

Both tank(over 800# w/ sump ago, rock, sand stand etc.) and man are roughly 200 lbs/ft. I'm sure it's designed to handle much bigger loads than that.

The full steel tub cones to mind, or a coach of people.

 

BTW, the bottom of the stand is constructed by 2x4s with this configuring if you were laying underneath it:

 

As said before load bearing wall and perpendicular to floor joist and you should be golden. You can pull up your carpet somewhere and see if you have concrete floors. I have a 125 on second floor.

 

I do have concrete floors, but it is the foam-crete stuff that provide no structural support. In fact, it adds more of a load to the floor trusses and is used primarily for acoustical reasons.

Having said that, I am leaning towards setting up the 20 gallon again in place of the 55.