An Irridescent might get to 3 to 4 feet in the wild but in a tank its closr to 2 to 3 feet. a 480 gallon (depending on footprint) should be enough.
ID Sharks are easy to get and not to mention that both of these fish do better in groups, so instead of trying to find 4 or 5 really rare fish you can get a group of ID sharks no problem.
