I would keep an eye out to make sure you can't see his inner body through the crack. If you notice that you can see it, it probably needs to be repaired. As long as you are seeing shell, its likely he will reinforce it himself. You want to try and keep him from being too terribly active and possibly worsening the crack (like climbing decoration and surfing down and possibly banging into something). The temp is great where it is. As long as he is eating well, I would keep his diet the same.