I had a light rail on the metal halide for my main display, it may be one of the ones that the OP was talking about. Since trying it, I loved it, and so did the corals, so I also want to do the same with LED's... but Im going to take it a step more:
Just like a CNC router, you can rip the motor and control components out of an old inkjet printer to make a computer controlled light rail for LED's. I figure I dont want something big and bulky over the tank, and LED's dont need one of those huge light rails, so... Im trying to program an Arduino to control an inkjet motor. That way, I can have the light wizzing back and forth like the light on a Xerox machine, or I can set it to move slowly throughout the day like the sun... with a computer controlled light rail, you can do whatever you want.
The change-up that I want to try is to use narrow beam optics on the LED's... as tight as I can get (5 degree or less), and have them stationary at one end of the tank shining parallel with the water surface. Then I can just use a small piece of reflective aluminum on the light rail to bounce the light off of and down into the tank. This way, the LED's can stay stationary and the light rail only moves a small square of aluminum. The spread of the light can be controlled by bending the aluminum then to create any light field with the LED light bouncing off of it. This method also allows multiple rails with multiple reflectors to be programmed... you could have them all moving as one or split up the beams across the tank. I also want to try controlling stepper motors on a turret style reflector so a rail may not even be needed, but thats in the future.
