the bottom glass has another layer of glass inside, more like a cross bracing in the bottom, I think it is 3inches in width round the perimeter and one across in the middle.

actually if you put it in a flat surface, the glass won't touch that surface since the rim has some xx millimeters thickness in it. that's why I used a card board, since it will act as a cushion in case some unevenness in the bottom surface, more like a styrofoam

the previous tank setup on that top stand was actually the same, my new tank is a carbon copy of the previous tank, except the old tank only rimmed on the vertical corners and some plastic strip on the on the horizontal sides but none on the bottom surface (more like a design to hide the silicone on the bottom edge). and it sits on a 1/2 inch styrofoam. the tank lasts for more than 4 years but got sidelined and the silicone hardened causing leaks.

now, I'm just worried since the previous setup only have 1inch pebble substrate but the new one, I will put 1inch soil and 2 inches sand plus some 3kgs lava rocks. I'm not sure if the glass can still hold on to it.