[spoonman]

I dont know how you can do it, but I would try to make something that would be wedge shaped that would take up the variance as you go from one side of the stand to the other. If you only put a block under one end of the tank to level it, the stand wil eventually sag and you will end up with the same problem. It needs to be supported along the whole length, not just blocked up on one end. Might be easier to take a piece of wood that is 4' long and cut it at an angle that is 1/2" higher on one end than the other then screw it to the front and back of the bottom of the stand, then the 1/2" block on the end. Is that clear as mud? It would look kind of like a realllllly long doorstop (or a shim).