These new T5 lights provide more light output than T8's.Actinic 420 promotes the growth of zooxanthellae algae, essential for the growth and well-being of all live corals and invertebrates. Combine with Zoo Med's OceanSun for a more subdued deepwater" tank effect. Combine with Zoo Med's UltraSun for optimum viewing pleasure of live fish and corals. Distributes the light evenly across the water surface. Generates less heat as compared to metal halide lamps."