Hey Angela,
I think what block head was trying to tell you is that the new "cube" tanks do no have center braces.
I have your exact light on my 30x30x24" cube. I hang it over the center of the tank with a couple metal hooks that come up the back of the tank. It spreads pretty good, but is still a ton of light. Par measurments in the middle center were in the 400-500, while the bottom front has a zone of around 100 par for my Scolymias.