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are metal halides and halogen lights the same???D


shadofax69

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Ok I had a thought. Im a chemist so when I see metal halide I know it has some sort of halogen atoms in it. So since a metal halide has halogen in it, are metal halide and halogen lights the same. I know the spectrum emmited from the bulb is probably a little different but I wanted to know if regular halogen work lights you get from lowes would work for a light source for any reef aquarium.

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They'd probably work for macroalgae and stuff but as you said the spectrum isn't designed to be what corals need and thus they don't really fare that well, they might grow but color, forget about it.

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MrConclusion

No similarity between the two light sources.

 

Metal Halide lights, and HID (High Intensity Discharge) lights in general, generate an arc of electricity through a semiconductive reaction chamber. The power is not flowing through a light filament, it's passing through a mixture of metal and inert gasses. There's not much of either because the reaction chamber is near vaccuum. The gasses support and influence the elctrical arc - different metals & different inert gasses create different colored light. The output can be extremely fine tuned to desired spectra. Consider the efficient but unsightly yellow of a sodium-vapor street light compared to the icy blue-white of a xenon HID headlight on a luxury car.

 

"Halogen" lights are just high-class incandescents. There's a solid tungsten filament that's glowing from heat, because it's very thin and you're pouring electricity through it. The inert halogen gasses surrounding the filament prevent it form burning up. If any oxygen gets in, as when a bulb cracks, it glows very bright for an instant before the filament burns out.

 

Halogen bulbs put out almost no spectrum that is useful to photosynthetic plants or animals. Your average 100 watt incandescent bulb has less than 15% of its output in the "useful" area of the spectrum. Also, halogens produce less than a quarter of the light-per-watt of most HID bulbs. Of the 100 watts you put through a regular light bulb, 91% turns to heat and only 7-9% is light. "Halogen" incandescents are more efficient at up to 12-14%, but fluorescent bulbs can reach 30% efficiency and HID's can exceed it.

 

You will read often of corals and other animals liking light in certain spectra, which are labelled by their color-temperature in Kelvin (K). The lowest K fluorescents or Metal Halides used for reefs are 6500, while 10,000 and 20,000K are even more common.

 

Halogen lights are 2600-3200K, and the 3200K are specialized photographic bulbs with very short lives. Nice commercial bulbs are in the near-3000 range. They just won't cut it for reef use.

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