You could use two rows of AH Supply light, like 3-36 watt light kits per row, 6 total. keeping about 8 inches or so between the rows. That would possibly be a bit more light than you could manage without CO2, but if you mounted them in a simple box hood, so they were about 4-6 inches above the top of the tank, it should work well without CO2. Or you could use a 96 watt and a 55 watt in each row. At worst you might decide to run only one row of lights at a time, to keep the intensity down.