I bought a 403nm Ecoxotic Stunner strip. There is short a video in the bottom right corner and you can see how they are easily installed and an example of that wavelength strip on a tank:
http://www.ecoxotic.com/products/modular-led-lighting/stunner-led-strips.html
It's a deep dark purple that makes colors in corals and fish pop in a different way than blues. I wanted something different and something that is not as bright because the tank is in my bedroom. I have an RKL with ALC module so my Blues and Whites ramp down on the timer and my moonlight turns on about a half hour before the others start ramping down. It transitions from full blue and white on to blue to purple. You start to see the purple as blues are at the end of ramping down. I think it gives it a cool look and it gives you enough light to see the creatures that hide all day start to come out. I only run it for about 2 hours after my blues are off because someone suggested that it might cause an algae bloom if left on all night, however I don't know how true this is. I have no explored syncing it to lunar cycles, but seems like it would be a cool idea if possible.
I should also add that it is not too intense and gets drowned out by the other lights so it would not be a good accent light if run during the daytime..