Light mover question

I am in currently in the planning stages of a frag tank system. I was thinking of using two 50 gallon Rubbermaid stock tanks and putting them next to each other. I wanted to use one 250 watt metal halide in a Lumen Bright Large reflector for my lighting. In order to cover the two tanks I planned to use a the Light Rail 3.5 6RPM motor. How long should my light cycle be? The light can travel the 6 foot distance in 6-7 minutes.

 

That is quite the system for moving the lights.

Are you thinking of making multiple trips down the rail a day or just one trip? If just one, then I think I'd start with a light cycle much like I use on the tank with 8 - 12 hours a day for each tank...

 

If I remember correctly, the large reflector has an effective range of 24"... Therefore approximately 1/3 of your tank will be lit effectively at any given time.
Length wise, all points greater than 24" from the edges will have effective lighting approximately 1/2 the time.

I am not saying you should double or triple your photo period because that is not needed... but I'm just shedding a little light on the matter as to how the tank will be lit. If I had to recommend a time, I would go with 10-12 hours