I'm am going through the process of specifying my new aquarium and thought the collective knowledge found here should make my problem a snap! The build is 1800 Long, 600 Wide, 450 Tall (MM), (Max of 425mm waterline) in a braceless design. Due to material cost and overall dry weight, I am stuck between two thicknesses of glass. 15mm & 12mm, with my preference being 12mm. As 15mm nearly doubles the cost and adds another 30KG to an already very heavy tank. Using the Aquatools glass thickness calculator I am being present with a safety factor of 8 for 12mm glass & 12 for 15mm of glass. Which are both incredibly over the safety factor of 3.8, which is an industry recommendation. Which I do not believe relies on a brace, as it is geared off the tensile strength of glass and its flex limitations a long a continuous span. Please let me know your thoughts!