Call me crazy (most people do).
I have access to sheets of acrylic that are 31" x 31" x 1/2" for $10.00 per sheet. I started thinking about what I could build with it. While this is very preliminary, I am curious what you expert DIY guys thought. Would the miter joints hold up under the water pressure for a 24" tall tank. I would hide the joints in the back wall behind the dual overflow boxes and beef them up with a second 6" wide layer of 1/2" acrylic. I would build a base frame out of 1/2" which would support the bottom panels as well as beef up the joints in the bottom panels. I would duplicate the base plate to create the top supports.
Ok, get your shotguns out and start blowing holes in my rough idea.