It is not uncommon to see cars replaced their halogen lamps with Xenon High Intensity Discharged (HID) ones. Am not sure this is legal, but I wonder whether such HID lamps could be used for planted aquariums. It seems HID lamps come in a range of colour temperature, at around 4000 lumens and last 3000 hours. The HID ballast has small footprint and use 12Vdc, though it requires high current draw when fired. Has anyone done a technical and cost studies on the use of HID? Regards.