What I would recommend is to get some aquarium safe sealant and put it on the inside of the tank. This might work, but then you might have some problems in the future. As you can tell I am not an expert on this, but it is the only option that I could think of. You also might want to put extra sealant where the crack is. I would also recommend filling it with regular water in the morning and watching it for at least one day before you start your aquarium.
Good luck.
Scott