I have a 125gallon (6'x18"x21") in the 2nd floor of my house, a 75gallon in the 2nd floor bedroom and a 20gallon in the same bedroom.
The key is to place it in a perpendicular to the joist and make sure the tank is sitting as close as possible to the exterior wall and this exterior wall must run all the way down to the first floor without any windows downstairs that stop the run. Also, make sure the tank stand bottom flat is all the way around (to distribute the weight evenly), not sitting in 4 legs.
My house is built in 1993 and had the tanks running for over 2 yrs now.
One more thing, you will be better off with the 125gallon since it is 6' long and covers more joist than a 4' tank.
I did ask an engineer/builder about my 125gallon tank, and this guy builds houses. He states it should be ok.
The key is to place it in a perpendicular to the joist and make sure the tank is sitting as close as possible to the exterior wall and this exterior wall must run all the way down to the first floor without any windows downstairs that stop the run. Also, make sure the tank stand bottom flat is all the way around (to distribute the weight evenly), not sitting in 4 legs.
My house is built in 1993 and had the tanks running for over 2 yrs now.
One more thing, you will be better off with the 125gallon since it is 6' long and covers more joist than a 4' tank.
I did ask an engineer/builder about my 125gallon tank, and this guy builds houses. He states it should be ok.