I know this post is a little old, but 2PSI (pounds a square inch) is WELL below most any glass breaking point.
Most glass tanks, because the trim lifts them a little off of the stand/table, are only supported around the rim, and that is perfectly safe.
I have 70lbs+ rocks in my 75 gallon tank (granite...very dense) and I have never had any problems with them. I do cringe a little when I move then and I can hear them scratching the bottom glass (because of the sand...) but I have never/will never worry about breakage with them.
Glass is amazingly strong, especially when the weight is spread out. Like someone else said in this thread, glass is only vulnerable when it is:
a) being flexed (why it cracks in the first place)
b) expanding or contracting quickly (like when you pour boiling water into a frosty mug... shatter)
or
c) when a lot of weight is put on a small area
HTH
Most glass tanks, because the trim lifts them a little off of the stand/table, are only supported around the rim, and that is perfectly safe.
I have 70lbs+ rocks in my 75 gallon tank (granite...very dense) and I have never had any problems with them. I do cringe a little when I move then and I can hear them scratching the bottom glass (because of the sand...) but I have never/will never worry about breakage with them.
Glass is amazingly strong, especially when the weight is spread out. Like someone else said in this thread, glass is only vulnerable when it is:
a) being flexed (why it cracks in the first place)
b) expanding or contracting quickly (like when you pour boiling water into a frosty mug... shatter)
or
c) when a lot of weight is put on a small area
HTH
