Shed some light

Just like a kid that keeps asking"why?"... I have to apologize...But from all the info..Metal Halide is the the way to go..Hence the question..Why?..So this is what puzzles me.
1. Halogen lights...Very intensive ..so why not use them..If it's for aesthetics, that can be corrected with other bulbs?
2. Plane old spiral fluorescent bulbs..They also come in a intensive output and a 6500K spectrum..(ditto on the aesthetics)
3. What are coral really looking for in light ...Intensity?..Spectrum? or both ?
...Had to ask these questions, being thick headed that I am,...I just want to confirm that these alternatives might have some malice.

 

You really have to know where the corals in your tank are from in terms of depth. Obviously corals from deeper water don't require bulbs in the 6500k-10000k range because at that depth the water reflects the white, yellow, red, orange light spectrum from the sun. That leaves just the green, blue and purple light from the sun that penetrates to those depths. Obviously if your coral is of a shallow water origin, then the full spectrum is more to their liking. as far as intensity is concerned, again look at the origin of your coral. Some corals prefer subdued, indirect lighting or bleaching and other problems will arise. For example, Tubastrea, doesn't require strong lighting as it doesn't rely on zooxanthellae for nutritional support. It must be target fed to survive. Therefore intense lighting is not required. On the other end of the spectrum is Goniopora. It is very reliant on zooxanthellae, thus requiring intense lighting to survive otherwise death is prevalent. Obviously, their is a medium ground, where corals can adapt and grow under lighting not specific to their overall needs. For example, you can be successful at keeping Montipora Digitata under subdued lighting, however, the color of its polyps will be of a brownish color, whereas, if the same coral were placed under metal halides, you would see the brilliant greens, purple, orange color of its polyps.
I hope I answered your question properly!!!

 

Thanks Coral Reefer
I take from what you your saying, is that halogen lights would be O.K. for coral with light demanding needs, but the coral will look better under Metal Halides???
I understand about the loss of the color spectrum in relation to the depth of the water(same thing happens to lures when fishing deep water)...But a typical aquarium is around 24in. deep..and from what I see on this site..everyone likes the Halides for all types of coral.(because of their lumen output??)And it seems that if their coral is not so light demanding ...the coral goes to the bottom of the tank(The range can be that small that 2ft of water would make the difference??)
From what it seems like...any type of strong light source will do, it just wouldn't look as pretty???
I know metal halides are tried and true....It's just the trying to re-invent the wheel, in me that makes me pursue these issues. And maybe stumble over a cheaper alternative that is just as good as halides.

 

The other thing to note is the eye appeal of the lighting for your tank. Do you want to replicate the bluer spectrum or yellow/white, or somewhere in between? Alot of people tend to go with 10000k mh's and actinic's for their pc's. You are then able to replicate dusk and sawn and reduce the stress brought upon them by turning the light on and off all of the sudden.
Hope this helps!