I'm not sure but if I had to guess that light fixture does not hold six T5 bulbs. More like four. Either way it is way more than what is required for both your tanks.
I would suggest a good 2 bulb T5HO light fixture. One with good reflectors and ballast. If you search in the reefing communities you can usually find great fixtures for cheap. Don't worry about the specialty bulbs cause you can just buy regular 6500K or 6700K bulbs or whatever, for cheap at hardware stores. Put that baby on a timer and you are good to go.
Hope that helps