Hello from Sherwood Park, Alberta.

[angelfan]

I didn't build them myself but I have two 220's (72x24x30) one of which is 1/2" and the other is 5/8" so I'd say either or will do as long as we're talking glass and not acrylic. Acrylic I don't know.
May I suggest the use of starphire glass? I wish all of mine were starphire but once you buy it, it's too late.
I plan on building my next tank out of starphire as it is not green at the ends and also makes for a better view. More initial cost but I would say its worth it. Just a thought