[underseaworld]

A lfs has this lighting system over its 400gl tank. The tank depth is 36". He has two lights that are 36" in legth that move back and forth. It looks like it would be a good thing in the Fish hobby. This is a statement I found on the net.
Just wonder what you guys may think?
LIGHT MOVERS

Using indoor grow lights is a less than ideal substitute for the sun. Grow lights are obviously less intense and don't cover a very big area. Grow lights lose intensity very rapidly as you get further away from the bulb, which means that plants need to kept as close to the bulb as possible for the best possible growth. There are two major problems with putting the light very close to the plants, the coverage area of the light is diminished and the plants can burn if kept too close to the light. Keeping plants under a stationary light can also cause another problem. Plants that are directly under the light will grow better than those that are just slightly off to one side, resulting in a pyramid effect. To combat this problem you can move the plants around or you can move the light around. Moving the plants can be difficult if not impossible, so moving the light is the only option in most cases.
There are basically two kinds of light movers, linear and circular. Linear movers move the light back and forth in a straight line (most models have a pause momentarily at each end further reducing the pyramid effect), these work well in a rectangular shaped garden. The circular light movers move 2 or 3 lights around in a circle and are designed for use in a square or round garden.
The use of light movers allows you to bring the lights closer to the plants without fear of burning them and they allow for more light coverage (you can increase coverage by 25%-35%). Light movers also give your garden better light distribution, and sends light to the plants from many angles instead of only one as with a stationary light.

[underseaworld]

Here is a web site for it. http://www.discount-hydro.com/lightmovers.asp

http://www.texashydroponics.com/shop/home.php?cat=223

The lfs has Intelli Drive 3.5 6 Ft Light Rail Systems with the extender and also this Light Rail 3.5 Add a Lamp Package

[Ninong]

Movable metal halides have been used over reef tanks for at least eight or ten years now. They aren't common but a few hobbyists use them over really large tanks.