I actually started to read into this myself. Not only do I want to try and create some natural moon light, but also see my tank at night without using a flashlight.
After seeing the blue led moon lights for $30 a piece, I've decided to make my own.
I though the moons wavelength was around 470nm in water, so I ordered some blue leds that will put out about 472nm. Some wire, a resistor, transformer and a timer - and instant moon!
I should have the parts on hand and built by next weekend. I'll be placing four easy positioning lights hidden from plain view behind my main light strip.
I can already, in two days, see a difference in algae growth with only increasing my main lights for 3 hours. (from 9 to 12 hours on). We'll see if my moon does anything with algae, rock growth or my critters....