Cutting glass and bulkhead size

Hey everyone,
I am going to be drilling a back piece of glass for an aquarium. My question is, it cannot be tempers glass correct and if I am using 3/4" piping and the bulkhead is a 3/4" bulkhead, what size do I drill the hole?
Thank you for your time and help in advance.

 

Go to glass-holes.com they sell glass drill bits and will have the size you need.

 

Some tanks are marked. Many are nice enough to label the glass as tempered with a big visible sticker, but many do not make it that obvious. Many times there will also etched markings on the corners of the glass to show it as being tempered (but this can be obscured in fish tanks with the framing).


Some experts can tell just by the sound/feel of the glass when tapped!

But really, the best way, is to used polarized sunglasses, like another suggested. You can see black lines in tempered glass that evidence the heating process with polarized sunglasses where there will be no lines looking down non-tempered glass.

And a 3/4" bulkhead needs a 1 1/2" hole.
38-42mm drill bit.