I asked about this a few weeks ago, and was going to just line it, but decided to give it another try, using some epoxy (or whatever its called).
I really piled some JB water weld on the inside and outside of the crack. I just filled it with water......so we'll see if it works. Its more towards the top of the stocktank, so hopefully the pressure is less than at the bottom, and hopefully it will hold. Even if I have to do this every year, I will be happy. I did not drill a hole below the crack, so hopefully it still works.
The tube of JB Waterweld was less than $5.00.