Jasonanatal,
just remember the shark is going to get about 3 feet long, in the tanks your planning on putting him in he wont be able to turn around easily. The width of the tank you buy should be at least as wide as the fish is long. 125 is not even close to being a large enough tank for the duration of the sharks life. Im not trying to be mean, but if you think about it, it would be like living in a closet your whole life. Would you like it?