I'm not sure which light would be "best" for a high light 30 inch long tank. It depends a little on the front to back depth of the tank. If the tank is 12-14 inches front to back, a single light fixture should cover the substrate pretty well, but if it is 18" and more, I think two lights, or a single light, with two groups of two bulbs, with 7-9 inches between groups might work better. Or, if you want to hang the light above the tank, you could use a 24 inch long light with 4 bulbs. Then, there is always the LED option, too. You could also use a 4 bulb light, with two electric cords, and run the two front bulbs for half the photoperiod and the two back bulbs for the other half.