Reef Junkie: the breakin period is normal. Every MH has it. Some manufacturers pre burn their lamps but these cost more. Burn in should not take longer then 100 Hrs max. I only deal with GE, Phillips, and Venture MH lamps since I have a professional relationship with the dealers and I get a good price.
Everything comes down to money
I think that if costs were equal MH would be a better choice for a reef tank. But MHs are more expensive(PS Aquarium trade is really high in price) so people turn to fluorescent. I have a fluorescent fixture that I made for my sump. I did not need a lot of light for some live rock an some macro algea. IMO everything has its use. Fluorescent are a cost effective way to achieve efficient medium light levels.
Based on my limited info. reef creatures need a high level of light intensity.
Reef Junkie: When comparing lamps ask what the CRI is on each lamp. Studies indicate that light incident on the surface of the earth is about 6500K CCT. A CRI of 90 will give you a full spectrum source. A lamp with a CRI of 60 will have gaps in its spectrum which may or may not be "bad" for the photosynthetic creatures.
thank you for your time and have a good day
How a MH lamp works:
the center of the arc tube is where the arc is. Here it is so hot that the metal/halide breaks down and the metal emmits light at its radiating frequency. The metal and halogen move toward the cooler arc tube where they recombine(this is why MH are position dependant, it is convection that moves them). now the cycle begins again.
common halides(this is not nearly an exhaustive list)
Scandium and sodium iodides
dysprosium, holmium and thulium rare earth iodies.
the Rare earth mixture produces about a CCt of 5400K which can be tweaked.
indium will give more blue when added to the mix.
UV is emmited and some lamps use a phosphor coating(like the fluorescent) to turn the UV into visable light.
About starting, above 150W the starting method is similar to mercury vapor lamps, with one exception. depending on the halides present it may take a larger starting voltage for the MH lamp.
When starting the reason you sometimes see differnt colors is that different halides vaporize at different temps. The restrike time is simply how long it takes for the halides to cool to lower the vapor presure of the gas. There has been some work done on restrike that eliminates the need for cool down. This helps me more then you. When I design a building with a generator to power the lights it takes 10Sec for the generator to start and get running. The MH will have gone out. When the generator picks up the lights I need the MH to come back on right away. My point
dont spend the money for instant restrike lamps on an aquarium.
Also, if you are interested in dimming a MH keep this in mind. You need to turn the MH up all the way and keep it there untill all the halides are vaporized before you can dim it down. If you don't you may not get the right CCT or intensity. There is a latent heat that needs to be provided to change the state of the halides to a gas.
I am ramble man!!!
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I'm so skeptical, I can hardly believe it!
