I asked ol' Rolf himself. This is the reply is got:
Subject
Tempered aquarium glass?
Discussion Thread
Response (Nathalie) 09/28/2006 08:10 AM
Dear Franklin Shiu,
We thank you for taking the time to contact us.
On all of our aquariums we use non-tempered glass. We hope this helps.
http://www.geosystemaquarium.com/geoeng/index.php
Sincerely,
Nathalie Bourassa
Représentante des consommateurs
Consumer Representative
Rolf C. Hagen Inc.