This shows you how importiant the spectrum of the bulb is to lighting. These are all florecent bulbs that screw into incandecent housing (regular bulb). The top and bottom are the (good) 19w 6500K (can be got at HD).. the mid one I accidently put in a 29w normal florecent... you can see the cruddy yellow tint to the light. Getting the right bulb goes a long way to making your tank look nice.