For the OP: I would be very cautious about using/repairing a tank with a crack on the bottom, for all the reasons stated above. Water is heavy. Add gravel, rocks, decor, etc, and that is a lot of stress on the bottom of the tank, which will be focused on the crack. I'd wait for the dollar/gallon sale at petco and get a new tank.
For Aquaman: Awesome tank, but I'd be worried about the integrity of the bottom for the same reasons I mentioned above. The joint is a weak spot, and with the 'patch' glass, it introduces additional stresses on the underlying pieces at the edges of the patch. That being said, it appears to be rimless and sitting directly on the surface of it's support structure, which would render my prior comments moot if true. Can you build me one?