I am no authority on this, but this is how I guess it could be done. Since you are importing species across international boundaries, and since it is international trade, my guess is that you would need a CITES permit. If these are legal animals, and, if they are corals, they may have to be captive bred, you would need the permit to show that they are approved for export. You may also need some sort of certificate to show that the specimens are healthy and not carrying any sort of pathogen. You may also have to find a way of making sure that they are quarantined on arrival. This is all speculation on my part, as I am comparing this with the importation of plants. Regardless, I think you would end up incurring so much more expense, and possibly extra time, that I doubt it would be worth it in the long run.