You have to understand that the wattage on your light has to be the one that fits your tank size and the use. If you want to have a growing reef you need between 4 and 8 watts per gal. depending, on your water depth and the type of coral ect. I went with the 8 watts 3x400 to give me the option of running 1, 2 or 3 lights depending on what I had in my tank. remember that the ballast is made for a certain wattage, but you can very the light color by replacing the bulbs i.e. 10k, 15k, ect. Make sure you specify what bulbs you want when you order it.