Moonlight

LEDs are pretty easy to wire. It just take a little internet research and patience. I have a bunch of LEDs I got for cheap off ebay. They are close to the same wavelength as the moon, and they put out an amazing shimmer in the water.

I've also heard of people having good results using cold cathode tubes.
 
There is nothing special or new about moon lights. Most any LFS or online fish store should have them. They are usually pretty expensive unless you diy, like all the suggestions above.

Basically put a dim light over your tank. Thats it.

On a big tank some use very small regular flourescent lights, sometimes actinic for the blue look. Most of the time they are LEDs. Sometimes CCFL. Some folks use submersable lights like you'd put in a pond. Most like blue. Moonlight is actually white, 4100K avg though. It doesnt matter for us, use any color you wish. Good luck.
 
Does anyone who uses these have issues with it screwing up your fish's nocturnal habits? I wouldn't mind getting something, but I don't want it to be super bright. (red is kinda appealing to me for that reason)
 
Usually the idea is that it is for the nocturnal fish, since they dont often come out during the day, by using a dim moonlight you can see them come out at night. I suppose it may interfere with nocturnals if its too bright, so just dont go wild with moonlights. Shouldnt be that hard to dim if they do end up to bright.
 
AquariaCentral.com