Led lighting is very different from conventional sources which generate light of frequencies all over the spectrum. LED is mostly monochromatic so the light is more intense at the specific colour of the diode, compared to other light sources. To get bright white light from Halogen sources you need to have very high powered emitters (ie: 400W) as 90% of the power used is manifested as Infrared (heat), UV and non white-light frequencies. LEDs are also low voltage devices so are a lot safer to have in the moist air above an aquarium. When run with sufficient heat sink, LEDs will last for years (7-8yrs) of actual usage. Given the lights on most aquariums are not left on overnight (allowing the fish time to sleep) that life span equates to >10 years in most cases. It is hard to find an alternate source as reliable - That's why things like the Space Shuttle, etc use LED lighting exclusively.