When selecting the wattage or color spectrum of your lights, keep in mind their location over the rock structure below. For example, placing a 10,000K high PAR emitting metal halide over a rock submerged only a few inches below the water makes almost no sense, especially when you have corals almost two feet down that need as much light as they can get. Place bluer, less intense lights over shallow parts of the tank and brighter lights over the deeper parts. Also, don’t waste the light on areas where there are no corals. This means you can actually use shorter light fixtures than the length of your aquarium, since the ends don’t usually have corals.