depends, how high above the tank? Are you planning to use any optics?
Either one of those will be fine depending on height and optic choice. If you want to figure it out for yourself you can use a right triangle using half the known optic angle with the height above the tank as the adjacent side of the triangle, you will get the result of the opposite side, double that number and its the diameter of the circle that will be projected on the water surface.
im not too familiar with the actual size of that tank but based on a quick search of dimensions, with no optics either layout should be fine.. perhaps evil has more insight.