Uhhh, is this bad?

[fkshiu]

Not sure how thick the bottom pane is. The tank's out in the shed and it's too late to head out there with a ruler. I cannot think of what else could have caused the crack, especially with the foam underneath. I took great pains when building to stand to have it perfectly flat and level. I even had a new concrete base poured on top of the uneven foundation to ensure level. On top of that I used an isolation membrane to negate any shifting due to the new concrete curing. On top of that I used porcelain tile for its greater strength over ceramic. In other words, it could not have been what was under the tank.

spencerC, I would not be too concerned about this occuring to you as long as:
1. the stand is properly built and level
2. you use foam underneath
3. you use HDPE plastic to protect the bottom pane of glass.