Since there's been some question as to how this operates, here's a picture of mine right now running the light on my 55g. You can see I just have it aimed at the factory IR receiver on the Current fixture. The remote still works if you want to manually change the mode, but if you don't touch it, the Arduino automatically changes modes according to the times you set up in the sketch.
The box underneath the Arduino and Current receiver is an old DSL WiFi box that I have gutted to use as a case for this project.
Note that the range right now is around 2 feet, I only have it this close for accuracy during testing. In the near future, I hope to extend the range to around 10 feet (the same as the factory remote).