One house plan that we like a lot has the office sharing a wall with the garage. One nice way to layout the large tank would be to have the tank resting on the garage floor, but viewable from inside the office. I think that would solve a lot of issues with weight, access, and humidity.
But my wife is rightfully concerned about such a large tank. If we ever moved, decided to renoovate, etc then the tank would be a HUGE obstacle.
But 12 feet is so sweet!!! That type of length would actually let me having a breeding pair of small-medium sized cichlids and see some somewhat natural behavior.
Many very large tanks are in garages. With your 48" width, getting the tank through a standard door opening can still happen by turning the tank on its side. But if you are going that big, why not go with a taller tank? If you did that, though, you would need a garage door, french doors or a sliding door to get the tank inside.....probably the main reason these big tanks are so often in garages. You mentioned moving...another reason to keep the tank in the garage, especially if you decide to go taller. An in-wall tank would be stellar. Here is a build with a 4,000 gallon tank in the garage, but viewed in-wall in the house:
https://www.monsterfishkeepers.com/...llon-tank-install-h20-custom-aquatics.187624/
BTW, that tank is now owned by bigrich545.
I have a large tank which is still not set up. We will never move, or if we do, the tank will not be coming with us. We have no door openings that the tank can fit through. The outside wall and windows were completed after the tank was moved inside..... At least two walls would have to be destroyed to remove the tank intact......a good argument for the tank in the garage....

