I believe that structural glass aquaria don't work above about 3' deep
- beyond that, the silicone doesn't have sufficient strength to hold
the joints together. If you go bigger than that, you need a frame
that takes the loads, and the structural behaviour potentially becomes
quite different.
regards, Ian SMith

Right... from what I've found so far reinforced concrete would
probably be the proper material for the tank, with the exception of
the front window. Of course, it would take a hefty piece of glass or
acrylic (probably glass?). Not to mention sealing it... I'd imagine
the concrete would be covered with some sort of epoxy or other coating
similiar to that used for in-ground swimming pools. At 7' high, 10'
wide and 4' deep it would be something like 18,500 pounds. I'm not
sure if that would sink into the ground? Center of gravity would be
kind of high too.

This school had one, it was probably 16' wide, and 8' deep at least.
It looked like the water actually went above the window, but there is
a possibility the window was just masked off.

Still digging, there is zero information about such a thing. I'm
surprised no one has attempted it?