Depending on where the crack is and how big, you may be able to patch it, rather than replace the entire bottom. You would also need to do a re-seal to the entire tank. that is still less work than replacing the bottom, which would also require a re-seal. Since that tank has no bottom trim, if the bottom is well supported, there should be no issue.
If that is the crack I see, a piece of glass that covers the crack and extends a few inches on both sides will be more than sufficient. It will be much cheaper as well.
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