Future frag room set up help

[kuatto]

Have decided to set up a room of tanks dedicated solely for frags and need a little help with the layout.There will be 2 possably 3 racks with 4 tanks on each rack.I was thinking of running either NO or VHO(24 inch bulbs).If I was to run 3 over each tank,would I need a ballasts for each tank or could I use fewer ballasts(just bigger).I'm just trying to wrap my mind around the idea of how things should be set up.
The frag tanks would be mostly zoos,rics and other softies.