DC aquariums up here said 10mm for a 450mm cube, braceless, opti-white.
Which surprised me somewhat as i was going in based on looking at thinner ADA tanks and my P@Q nano opti which is 5/6mm i think....
Are there not several suppliers of "opti" type glass? Would they not all have different recommendations dependant on the flex-strength and load testings of their specific low iron glass formula?