Built a similar sized and shaped tank in 2000. Used 2X10mm laminated glass with top and bottom bracing, as well as cross-bracing. Bottom bracing was to prevent bowing, as well as to give the glass a bigger surface area to bond onto as the pressures on the glass were high due to the depth of the tank. The tank had to be built in-situ due to the weight of the glass. Tank was 900 deep with 2 X standard 1.2m tanks as sumps, of which one was a refugium. Very important to screed the surface on top of the lintels perfectly level, otherwise the base will crack in time due to the weight of the full tank. To access the centre of the tank, I had to build a removable reinforced board that would go across the top of the tank that could support my weight. I would then lie on the board to do any work/maintenance in the centre of the tank. Lighting was a metal halide system 4 X 400W (In those days Eskom still had the cheapest electricity in the world!) I ran 2 Red Sea Berlin skimmers as space under the tank was restricted. My overflow box that measured 300 X 300 was filled with Bio-Balls to silence the water flowing out the tank. Shut the tank down in December 2018 and broke it out so that I could repurpose the area to be able to sell the house.
Good luck with your build. Large volume tanks are so easy to maintain if you have done your research, planning and design properly. I never did a single water change in17 years!