Insulated glass? Meaning there are two panes of glass with a strip or swiggle separating them and probably argon gas filled? To be able to use on a tank 33" tall, each pane of glass would need to be pretty thick. From the sound of it, you probably have 1/4" panes and half gap. If so, I would not use this on a 33" tank. You can always split the panes and build shallow tank. As far a tempered goes, yeah you can use tempered glass on tanks. Lots of companies do it everyday, especially on the bottom panes.