Seeing it may be out of warranty, guessing for not sure when you purchased and if it was new, you may be out of luck getting help with replacement costs I am sorry to say.
If costs are to high for you to replace it at this time, You may care to empty the tank and make sure the crack area is dry (hair dryer) and then try to use epoxy to seal it. It should both seal the crack and also help to keep the crack for continuing.
(Just a suggestion. Other products may be on the market for this. Epoxy was the first thought I hand based on stopping the leak and helping the strength. Note, not sure if you had worked with epoxy before, but once you mix, you have little time to apply.