Well I picked up a cheap pair of polarized sunglasses at Target today. Just using polarized sunglasses it was hard to see the marks in tempered glass unless the lighting and the angle was just right.
I did more searching online for a better technique and found this.
http://www.salt-city.org/showthread.php?t=9542
Using my laptop and the polarized sunglasses I was easily able to see the tell tale signs of tempering in every car and house window I tested. However using this method none of the panes of glass in the tank appear to be tempered.
So Aqueon says the bottom is tempered, the dude at the glass shop thinks it's all tempered and as far as I can tell nothing is tempered. I'm tempted to take the gamble and drill the bottom of the tank. $150 is an expensive bet for me, I like to stick to the $5 tables in the casino.