They can get 4' plus, so I would think at least a 12'x4' tank would be needed for an adult. Not many people have kept them though so its tough to say how big they might realistically get in captivity.
I've heard that Tiger Musky are fastest growers than their pure parents as they don't live longer than a pure musky. Find a food source for a super-sized predator can be tricky but Tiger Musky do well on pellets at the hatchery.
no way i just vacationed at fernandina beach! Is the surf still full of sharks around beach restoration areas? I saw some big 6 foot sand sharks in the evening about 10 yards of the beach