Depending on where the crack is and how big it is…Any number of materials can work. A possible draw back to sealing a crack is that some finish breaking at a later date. If your crack is in an area of stress (like around attachment bolts or where the trip lever goes through the tank) I wouldnt take a chance on trying to seal it. There isnt a lot worse than a toilet breaking apart unexpectedly. And the pieces are like knives. On the other hand, Ive seen repairs that were many years old. Good luck.
