Perhaps because the greatest load is on the bottom plate. From the
comments above, I thought it strange to read that tempered glass was a
no-no when I've had numerous tanks using tempered glass. But maybe the
float (plate) glass are used for the walls only. I couldn't remember the
stickers I read being specific to which part of the tank was tempered.

The op didn't make it clear on stress/strain factors or ratios. But if it
helps, within a given dimension, tempered glass is far stronger than
stainless steel and the stress/strain ratios are linear.

HTH.
-ED


I look at it in a very simple way. Would you rather 100 gallons of water in
a steel box or a tempered glass box? Steel flexes, just as normal glass
does. Tempered glass shatters into a million pieces at the slightest
bending out of shape. Take a look top down at your tank. You'll see the
glass bulging out near the center. If that was tempered glass your feet
would be wet and perhaps missing a toe or two The reason they use
tempered glass on the bottem of tanks sometimes is because normal glass
flexes. Being at the bottem there is a lot of pressure and normal glass as
stated above will flex quite a bit. This isn't good on the bottem because
the seams and seals with soon part and now you have a leak. I know this is
contradictory to what I said above, but if you stop step back a minute and
think about it...What is under that tempered piece of glass just above the
stand? It should be wood or some other semi-tough material bracing the
glass above between the stand below. The glass doesn't flex because of the
brace and it won't shatter.


Sean