Photo's of the finished inner frame assembly are below. It just needs final painting. The pocket holes in the shape of a V are for mounting the side panels to the frame.
The parameters I have to meet is that no wire or plumbing can be seen hanging off the back or otherwise. The water level at top of tank cannot be seen and the side of the gravel or sand bed cannot be seen. This was set down by the other half. I had to get an OK for the wires and cables to the wall plates. This included 5 tubes from a wall plate to the tank. I am glad I got a signoff on that otherwise this would not be possible. So this design is to keep as much as possible hidden from view. Now ...