I acquired a 150 gallon glass tank from a friend of mine. I would like to drill the bottom for a Herbie and my returns. I know that some manufactures make their tanks with tempered bottoms. I tried the polarized sunglass thing and I can't really tell much difference between the bottom and the sides. I suppose the whole tank could be tempered or I could be doing something wrong. The glass all looks smooth and I do not see any waviness to the glass like I have been told I would see with tempered glass. I don't know who made the tank but the stand that came with it is a Perfectaflo. The glass is about 7/16" and it has a faux wood plastic rim around the top and bottom. I do not want to run the standard over the side overflows. Any suggestions?