u/Ripley-8

Hi dad, so like the title says, the tank for my toilet cracked and im unsure how exactly to fix this. I dont know how to attach a picture but its on the front of the tank, about 8-9 inches long going down from the top. It was leaking all over the floor which is how I noticed. I turned the water off and put a board in between the plug chain thing to keep it from filling back up, and I bought some J B Weld boat fixer (I figured this would be okay to get wet after it cured), but im not sure if I did the right thing. Will this work? Do I have to replace the toilet? Is there a better product to use? I thought plumbers poxy was for pipes and stuff so I didnt get it, but would that have been better?

Thanks pops.