I wouldn't keep it with anything. Large or predatory fish will eat it, small fish will be eaten as soon as the shark hatches. Mobile inverts like hermits might help--they would likely just keep the outside clean without damaging the egg, but they too may become a snack for the baby.
Size aside, sharks really don't do very well in captivity. An LFS used to have a large nurse shark in a huge tank, and the poor thing just circled the tank constantly. It's nose was a mass of scars from banging into the walls all the time. I felt bad for it. They finally had to put it down, when the tank broke.
Just a pathetic existance for such a cool creature, IMO.