The Kessil A160WE Tuna Sun LED Aquarium Light comes with two control knobs. One knob is used to control overall intensity and the other knob the 6,000K/9,000K LED spectrum mix. You can tune a preferred color within the spectral range thousands of research and testing hours determined to be the optimal spectral points. In addition, you can control the A160WE with the Kessil Spectral Controller (a separate purchase). This version is designed for use with planted aquariums. For reef aquariums you can use the Kessil A160WE Tuna Blue LED Light Fixture. 40 Watts: Effective light equal to a 175 Watt metal halide. Variable Color Temperature: Using the color spectrum knob on the top of the light you can tune the LEDs to your desired color temperature. 6000K? 8100K? 9000K? No problem. Can be controlled with the Kessil Spectral Controller (a separate purchase). LED array specifically designed and tailored for freshwater planted aquariums.