He might only have 8 or 10. He used ot have a whole bunch of VHOs (like 5 years ago) but has since upgraded to T5s.

He has always AFAIK had lots of flourescent lighting.

Yes, you need a min of 2 feet above a tank IMO to do a light rail and still have room to work. 3 feet is best.

[quote=With a 6 foot tank (halide between 6 to 10 inches from water) and one 250 halide there would be a couple of options:

1) most popular because all of the light rails I have seen move back and forth with only up to a min delay in between moves. the corals (as individuals, not as a group) would see light then very minimal light then light.......

2) get a light rail that moves the light across once in a day. the corals will only get a couple hours of intense light per day.

Make sense now?[/QUOTE]

Why not a little bit of column a and a little bit of column b?
one travelling end to end in up to a minute running simultaneously with one that travels across once in a day?

just curious, not very lighting savvy...