# Why one blue and one white?



## bigfishy (Jun 19, 2009)

Why does a reef aquarium's fixture requires a white light and a blue light to it? Can't it be just all white??? 



What does the blue bulb do?


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## PACMAN (Mar 4, 2010)

It has to do witht he light spectrum. if you want corals, they require a certain wavelengths, which is usually where the actinic (blue) bulbs come in.


if you are going to keep a FOWLR or FO tank, then the blue might not be necessary.


Someone with more experience will probably chime in and elaborate/correct my post.


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## wtac (Mar 17, 2006)

You are right on the wavelengths, PACMAN .

The white bulbs gives what the corals need for photosynthesis (PAR) and the blues predominatly for the color "pop" and very little wavelengths for photosynthesis. T5 bulb temps (same for PC bulbs but only see them available in 10,000K and actinics) suitable for reefs range in 10,000K to 22,000K. What you choose really depends on desired look and growth rate. Generally speaking, the higher the K value, the lower the PAR value.

Today, there are T5-HO actinic bulbs that have other phosphor blended to give some PAR value. The better bulbs in this category are ATI BluePlus, KZ SuperBlue and Geismann Blue+

HTH


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## PACMAN (Mar 4, 2010)

Thanks for the correction Wilson!


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## bigfishy (Jun 19, 2009)

wtac said:


> *The white bulbs gives what the corals need for photosynthesis (PAR)* and the blues predominatly for the color "pop" and very little wavelengths for photosynthesis. T5 bulb temps (same for PC bulbs but only see them available in 10,000K and actinics) suitable for reefs range in 10,000K to 22,000K. What you choose really depends on desired look and growth rate. *Generally speaking, the higher the K value, the lower the PAR value.*HTH


What do you mean by that? I still don't get it! 

So a 14000k light won't give as much photosynthesis to a coral than a 6700k light? But a coral need that low nm wave of light + a low k value light for photosynthesis? Is that correct?


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## Big Ray (Dec 8, 2009)

bigfishy said:


> What do you mean by that? I still don't get it!
> 
> So a 14000k light won't give as much photosynthesis to a coral than a 6700k light? But a coral need that low nm wave of light + a low k value light for photosynthesis? Is that correct?


Dont over analyze it, there is ALOT of science behind all this ....

K value is named after Kelving temp. and it represents the color output. lower = more yellowish/redish, and higher = more bluish/UV.

PAR is the available radiation for photosynthesis. meaning alot is radiated from a bulb, PAR shows how much of it can be used for photosynthesis. it has nothing to do with K value.

so your statement "
So a 14000k light won't give as much photosynthesis to a coral than a 6700k light?"makes almost no sense, as the difference between 6700K and 14000K is just color output, not PAR SPECIFICALLY.

now let me explain it in easier terms. CORALS need light. they use light for photosynthesis. the higher the PAR reading of a bulb, the more photosynthesis-ready light that is radiated. that means the light wavelenghts (almost all) which can penetrate coral and make it convert sugar to energy.

Next comes the K value and colors "popping". the COLOR on corals that we see, is just a reflection of the light that is shined on them ! what does that mean ? if you shine yellow light on a blue paper, you will see green ! 
corals coloration work in 2 different states, one is th reflection of color shined on it, second is "How does such wavelenghts Excite the proteins inside a specific corals. " for example, certain proteins shine color of blue when Excited at molecular level, and it has been found that light, at Wavelenght of 420 nm, will penetrate and excite those proteins, which in turn will reflect back a florescent blue color.

so ure better off just assuming that, lower K value = better growth, higher = better coloration.
PS. let me know if you need sources or papers explaining more, but its ALOT of readingslol


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## bigfishy (Jun 19, 2009)

Is this what you mean?

Eg.

Let say a 14000k T5HO 39 watt bulb

39 watt is the PAR? the amount of energy radiate from the bulb? so the higher wattage of the bulb = higher PAR?

14000k is a color enhancer which react to the protein to make the coral looks colorful?

a blue bulb is a support of the 14000k to show more of the coral's color?


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## Big Ray (Dec 8, 2009)

bigfishy said:


> Is this what you mean?
> 
> Eg.
> 
> ...


Not really watt is power, PAR is light which can be used for photosynthesis ....

here, is a good read :http://www.americanaquariumproducts.com/Aquarium_Lighting.html

as I said above, there is alot more into it if you like to think that way....

and correction on my last post:
"PAR is the available radiation for photosynthesis. meaning alot is radiated from a bulb, PAR shows how much of it can be used for photosynthesis. it has nothing to do with K value."
PAR does depends on the K value and type of bulbs and alot more... . but you cant say higher K = lower par or anything like that.


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## bigfishy (Jun 19, 2009)

Big Ray said:


> Not really watt is power, PAR is light which can be used for photosynthesis ....
> 
> here, is a good read :http://www.americanaquariumproducts.com/Aquarium_Lighting.html
> 
> ...


OK! I will get back to you, when I finish work and finish reading

thanks for the link,


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