Many DIYers have found that they can increase the Safety Factor for a given thickness and tank size by installing a 4" wide glass brace from front to back of the top of the glass, essentially turning their tank into two 2' tanks, increasing the Safety Factor to 3.38. Rather than go to a thicker glass to increase the Safety Factor, you can economize on construction in this manner.
You can also economize by designing your tank stand so that it fully supports the entire bottom of the tank by using a styrofoam or polystyrene pad between the tank and stand. The pad will keep the tank from failing due to a point load on the glass surface which can be caused by dirt or grit on the stand surface. If the tank bottom is fully supported, you can also use a thinner than normal piece of glass for the tank bottom, since the stand will be adding strength and support, keeping the glass from bending.
Yet another trick is to compute the required thickness for the end pieces of your tank. In all likelihood, the required thickness will be less than the longer front and rear pieces of glass.
