LED lighting

In my view, LED lighting seems like the aquarium lighting of the future. The light-emitting diode, founded on semiconductor technology, appeared in the 1960s as indicator lights on the hi-fi, with their intense and piercingly pure red and green hues. Light-emitting diodes as sources of illumination started to be available in the 1990s. The technology has been taking off since  then, as light efficiency measured in lumens/watt soared from about 30-60, up to approximate the energy efficiency of compact fluorescents today. This "luminous efficacy" is increasing with each generation of LEDs, and reports indicate that the most recent high-end LEDs are currently approaching 250 lumens/watt. By 2015 LEDs'll be standard in household illumination, I reckon.
 
LED lights, purchased individually and set into systems that were rigged up as DIY projects, began to be discussed in aquarium forums in 2003/04. But many fishkeepers then and now were and are watching and waiting, as quality rises, technology matures and prices drop. 
 
Aside from the reduced energy costs and the decade-long working life of the diodes, which make LEDs "greener" than other lighting technologies, they produce markedly less heat, which was the convincing selling point for me. Others follow reefkeepers in enjoying the "moonlight" effect of all-blue LEDs, and the fact that they are dimmable. For me, the "shimmer" effect of point-source LEDs gives "glitter lines" to sunlit surfaces, which I wasn't even aware that I was missing before.
 
LEDs for aquariums are available as spotlights and strip lights. Currently the "white" LEDs are actually  blue diodes that energize phosphors which radiate a somewhat chilly-looking white. Tech is evolving rapidly here, too. 
 
In June 2011 I even purchased at eBay two primitive and clunky cheap panels of blue/white LEDs, in a pegboard array of bare LEDs without any secondary optics in the way of reflectors or lenses, as a way of dipping my toe in the water.  A better introduction to LEDs than these Chinese panels would have been Marineland's Double Brite fixture, which came into the market at the end of 2009, but which does not quite support the growth even of Cryptocorynes in an 18-inch tall 16-gallon tank here; I'd have done better to spring right away for Marineland's entry-level "Reef-Capable" system, with a denser diode array. Since then, I've made the substitution, and put the Double Brite over a 10-gallon planted tank, and both are thriving.