My tank is over 7 feet and I use 3 250 watt halides with the lgiht rail.

I don't think a 6 footer would work with 1 halide. It is not like the sun, where it changes angle but is always shining on the reef through-out the day.

Why not though, there must some measurement like lux or PAR/meter²/hour from a reef to match.

Wouldn't you have major shaded areas with just one halide on a rail over 6ft?

Let's take a reef at 9am and then again at 3 pm in Fiji for instance.

At 9 am the sun is at a 45 degree angle and then it is right overhead at noon and then again at a 45 degree angle at 3 pm. The sun would be directly hitting the reef for the whole 6 hour period (sure a cloud might block the sun for a while, but there would still be a high par value even then) just at diferent angles.

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?

If running a single small pendant would be thinking something that continually goes back and forth.

We are already playing games with algae lighting (24/7) and corals having spot lighting, instant off and on with timers, overall durations different than the reef, some people running 250W bulb and others 400w or T5s or different spectrum on the same species. Just wondering lightwise, how much we can fool the coral so they believe there under the surf in Fiji.

Also at what point would this be annoying to the viewer.

Jayson from SWC has a 300 gallon a 8 footer and has 2 mh on a rail a 175 and a 250....

Keep in mind that Jayson (who has the same light rail as I do) has about 12 T5s over that 300.

It is almost hard to notice where the halides are.

Oh i guess he added some more lighting to his tank I didn't know that

I agree that one MH on a rail over a 6' tank probably isn't enough. I had originally planned on 2 pendants along with supplemental T5 lighting for my setup. In end the low ceiling in my basement did in the light rail plan, but I'm still a fan of the theory behind keeping corals out of direct intense light 100% of the time.