For sale is a 72" light track for halide lighting that is motorized . Was installed on my old canopy to move a metal halide lamp from one end of the tank to the other to mimic natural sunlight over the reef and reduce dead spots of light in the tank. The track rail can also be cut to reduce length for shorter tanks. Here is a link to the model.
http://homeharvest.com/lightmovers.htm
$100 obo
Stan