everything i read on them says that and plus they dont swim a hole lot and thus can live in small tank but i wouldnt do anything less than a 150 my self
And there in - lays the problem. Especially if your reading an quoteing "Aquarium Sharks & Rays". I also was once "a Fan" of that Book - until I was shown the error of my way of thinking - by some people that are much more knowledgeable than Mr. Michael's is.
Keeping Sharks (or any thing for that matter) should be about more than just relying on what others have said. It's always wise to use common sense, and research topics before jumping in (And sometimes -I'm known for doing that as well). And quoting from a single source is usually a bad idea.
But as I stated before - Mr. Michael's Figures keeping sharks are grossly underestimated - to the point of cruel. Most of the shark species - he lists in his book should have a minimum tank size of at least 200% greater than what he suggests. And remember - it's not about volume -but surface area(footprint).