Safely drilling tank

[Bill B]

Hi there, I recently bought an older 3ft 50 gallon tank. No clue of who the maker is except the glass is a little thicker than any of my smaller tanks including 2 std 55's. I would like to drill the back since it seems that an external overflow is a little more expensive and prone to problems. Are there any clues to look for as to whether the back is tempered or not. It wouldn't be the end of the world if I drilled it and it turned out to be tempered, since I didn't pay much, but I would just as soon use it :} Thanks for your educated guesses.

Bill

[jestep]

I find the easiest method is using good polarized sunglasses or a laptop or cellphone to see if the glass is tempered. With the sunglasses, you can typically see colors and distortion in the glass when changing viewing angles. For the laptop/cellphone method rotate the screen behind the pane of glass and if it is tempered it will usually cause darkening or other distortion when looking at the screen through the glass. You should be able to find some youtube videos to see exactly what I'm referring to.

[Isaac]

9/10 times, only the bottom is tempered. other factors to consider is the age of the glass... the older the glass, the more brittle it becomes. the polarized glasses trick works well. stand infront of the tank, arms out, rotate the glasses slowly... if it goes from light to dark to light... tempered. putting them too close to your eyes, its harder to see the obvious shading (because your eyes are so close to the glasses, you essentially see through the lines somewhat)

[Bill B]

Thanks for the tips. I am more confident it is not tempered now!