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Why do the metal halide lights usually come with actinic lightWhat purpose dose the actinic light ha2007-11-24 23:43:54

I am going to keep one marine reef aqurium, the light is of vital importance. Can the metal halide lights simulate sunlight? If so, why do I need actinic light as well? need help.

Thanks in advance.

nuo

Answers:

Actinic lights are primarily for aesthetic purposes, although they do serve a practical function for certain invertebrates such as coral.

In nature, reefs are located generally from sea level to 40 or 50 feet deep. On average, 10 to 20 feet of water is typical. When sunlight hits the water, much of it is simply reflected away. Some doesn't and penetrates deeper in the water. Because of the wavelengths, the red end of the spectrum gets filtered out/blocked first. This is why red things (fish, coral, etc.) under water aren't very common, nor are they easy to see -- they look black without the red spectrum.

The blue end of the spectrum is the last to be filtered out -- hence the typical deep blue hues you see in underwater pictures, and a reason there are so many blue fish in the ocean.

Actinic bulbs mimic these hues, and make an aquarium look as if it is deeper than the foot or two under water that it really is. In addition, because the blue is the last to be filtered out, it is used by various invertebrates like corals and sea anemones as food. That is, the zooxanthellae in their tissues use the light as food, and their wastes (starches and sugars) are what feed the animal.

Hope it helps!

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The Halide lights simulate the sun, they get very hot. I have them set to come on at 10am and shut off at 5pm. The Actinic's run from 8am - 8pm. They bring out the fluorescent colors of fish and corals. They are great for transition from dark(dusk & dawn) to very bright(daylight sun).

Plus it gives you more time to enjoy watching your fish!

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if you are going to keep live corals the spectrum produced by the actinic lights will supplement the metal halide lighting. if you do not plan on keeping live corals the actinic lights are not necessary but they do help bring out the colours in the fish.