litterally just setup a rio240 in the lounge...
It was un-level to start with (empty) leaning into the room.
I packed the front of the tank and over compensated.. half filled and it was bang on level... filled it to the line and its about 4mm out front to back. along its length is fine....
The tanks in the shed are a different story. with the weight of all the tanks (15 at one point) the floor has settled low in the middle - the tanks on the far wall slant inwards towards each other by about 20mm. The 240 will mean that they are going to be shut down anyway.