styrofoam under tanks

[The Grizz]

With the sides, front and back glass sitting on top of the bottom pane of glass there is way more chance of the tank cracking under the weight of the side glass. All it take is to get one corner a little higher then the rest and you have a stress point. make sure that the bottom of the tank is sitting perfectly flat EVERY WHERE. A properly built tank has all side on the outside of the bottom pane, its called a floating bottom.