I had one unit on a 47gal column tank, 18”x20”. The new tank I'm working on setting up is about 65gal, but has the same footprint as your tank, it's just taller. I bought another AI unit and plan on running the 2 longways (is that a word?) It looks like it'll give great spread. I actually like having brighter areas and dimmer areas, so I'll adjust the positioning a bit to achieve that. Are you considering the vegas at all? I've read a few people mention thinking the additional color options really do matter to coral growth and coloration. Just a thought if you can swing the extra cash and are buying new units anyway.