[untamed]

Yes, you have dug up the past!

The weight of the upper walls is carried by the tank. However, there is a layer of that foamy door sill material between the tank and the walls. I did that primarily to prevent water from splashed out the seam.

Those walls are NOT attached to the ceiling. The walls are three pieces (left, right, front) They are screwed to each other and only screwed to the surrounding walls at the back left and back right only.

If you look closely, you might be able to see the foam layer in this photo. You can also see the bolts that connect the left and right frames to the front frame.