I started out by scoring a used, 27 gallon hex for 10 bucks at a local thrift store, and a hex end table of an appropriate size, for another 10 dollars.
This tank was exceptionally old. So old, that instead of a solid plastic rim that's standard now days, it had a pre-segmented plastic rim. I sliced between the two pieces, loosening the glue.
And slowly worked my way down the silicone surrounding the pane I was trying to remove.
Eventually, I had the pane mostly loosened.
And with some careful carving at the bottom, removed.
Evidently, I skipped a few steps in the picture taking process. But, after removal of the pane of glass, I cut it twice, once about 4 inches from the bottom, and once two inches from the top. My cuts weren't terribly straight, as I'm not terribly practiced in glass cutting, but I didn't snap the whole thing into a million pieces, so I ran with it. I sanded all of the cut edges with a 60 grit wet sanding block until all the rough edges were smooth, and the fit was easy to open, but tight.
Dry fit.
Then I turned the tank on it's side, and glued the top and bottom pieces back into place. As the glass was beveled, it sat nicely in place, with only a couple pieces of tape to keep it secure while it dried. I picked up a couple 1 1/2" hinges from the local hardware store, scuffed up te back with sand paper, and glued them to the door, and the tank. I laid the tank back on its side, taped up around the places I didn't want glue, and set the door into place, then just glued the hinges on.
This would have been much more difficult if the glass hadn't been beveled.
Which brings us to this picture.
You can see, the gaps between the door, and the frame are pretty tiny.
My closure method can be seen here.
I also made a top out of 1/2"x1/2" square dowel, cut to fit. Then I taped wax paper to the frame of the tank, set the pieces in for gluing, to get a snug, but not permanent fit, and painted the whole thing black.
I cut a piece of fiberglass window screening to fit the frame, and glued it on with E6000, which I pressed into the screen for a good tight seal. I lack a picture of that, though if you really want to see it, I can go pop it off the tank and snap a photo for you.