This might sound stupid, but if everybody here is worried about the glass breaking on the bottom, and want to replace it cheap, why not put in a 3/4" piece of marine plywood, fiberglass it, and paint over it. You could reinforce the plywood to make it stonger and less brittle than the glass, plus, it would be cheaper than tempered glass.
After all, it is on the bottom(who's gonna see it?), and I've seen tanks well over 1,000 gal using plywood.....It'll hold.....
After all, it is on the bottom(who's gonna see it?), and I've seen tanks well over 1,000 gal using plywood.....It'll hold.....