# 6700K or 10000K bulb



## maverick2402 (Jul 5, 2005)

I have a 10000k bulb and was wondering if I should stay with it or switch to a 6700 k bulb in a 20 G high tank with glosso amoung other light loving plants.The light fixture is a 65 w power compact.


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## Spar (Aug 7, 2003)

since it is 100% preference of the light color, a poll isn't really informative in this situation. which you do like better, 10000k (a brighter white almost blue color) or 6700K (more yellowish).

plants don't care either way, so it is which ever you personally like.


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## malkore (Nov 3, 2003)

agreed. either is gonna grow plants just fine. 6700k will look more yellow to your eyes than the 10,000K. the plants will just see light.


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## Left C (Nov 15, 2003)

Here's some more options.
Current has a dual daylight 6700K/10000K 65w bulb: http://www.current-usa.com/products/sunpaq.html
and
Coralife has a 6700K/Colormax 65w bulb: http://www.esuweb.com/products.asp?...Lamps&RelationID=12&IDProductRelationship=305

I have one of each in a 2x65w Orbit fixture. The color mix with these two different bulbs is really great looking. http://www.current-usa.com/products/orbit.html


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## DarkCobra (Jun 22, 2004)

malkore said:


> the plants will just see light.


NOT true. Chlorophyll absorbs light efficiently only at specific wavelengths. Google "chlorophyll absorption spectra" for more information. This is the reason that plant grow bulbs look terrible, but grow plants great at less wattage - because it's producing only what plants can actually use.

10,000K produces more blue and generally replicates the appearance of sunlight in deep ocean environments, which is a rather unnatural spectra for freshwater plants. Sure they'll grow, but there will be differences in *how* they grow compared to more natural lighting, due to the altered ratio of red/blue in the light. Those differences may, or may not, be to your liking for any particular plant. Plants will change color, node length, leaf shape, etc.


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## mrbelvedere (Nov 15, 2005)

Some say 10,000K makes their plants grow denser, but I couldn't tell you from experience. BTW, 20,000K will actually grow ambulia, crypts, and java moss quite nicely. That I do know from experience. If 20,000K can do it, I don't see why 10,000K is any worse than 6700K. I personally use a 6700K bulb with a 10,000K bulb. It's a good compromise.


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## malkore (Nov 3, 2003)

DarkCobra - I was offered 2 choices: 10,000K and 6,700K. Both are fine for plants...Kelvin is color temperature, not spectrum anyways, so the question itself is flawed enough that we don't have to get overly scientific.


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## Lorenceo (Jan 29, 2004)

But the color temperature is determined by the spectrums.
For example: A 10,000K bulb has more blue and less red than say a 6700K bulb. This makes the bulb appear bluer than the other. Make sense?


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## malkore (Nov 3, 2003)

Lorenceo said:


> But the color temperature is determined by the spectrums.
> For example: A 10,000K bulb has more blue and less red than say a 6700K bulb. This makes the bulb appear bluer than the other. Make sense?


then why is a 9325k so pink/purple, and an 8800k is so white, but so is a 10,000k with only a hint of blue?

Also, why did my 3,000k bulb grow java ferns like crazy?

cuz color temp doesn't equal spectrum


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## adamjh (Sep 2, 2005)

Maybe people should start rating bulbs by the quality of their spectral output then.:icon_roll Bulb X could be described as having peak wavelength outputs of A nanometers, B namometers, and C nanometers. Meanwhile bulb Y would have peaks at B nanometers, C nanometers, and D nanometers. I wonder if this would be more helpful.


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## Lorenceo (Jan 29, 2004)

malkore said:


> then why is a 9325k so pink/purple, and an 8800k is so white, but so is a 10,000k with only a hint of blue?
> 
> Also, why did my 3,000k bulb grow java ferns like crazy?
> 
> cuz color temp doesn't equal spectrum


I don't think the kelvin rating on those GE bulbs is correct tbh. Also, the kelvin scale trend isn't 100% accurate.
Same thing with the Hagen power glo tubes, they are rated at 18,000k but are pink.

Because that is their kelvin rating. Also, your eyes will adjust to any color temp as "white" (and so can your cameras white balance) I've read reefers posts saying that they see their 20,000k bulbs as white, 10,000k as yellow and 6,500k "nicotene teeth" yellow.
And that is a quote from Pies on FNZAS. View that thread  here

Perhaps this scale will help.








I stand by my statement that color temp is made up of the different spectrums put out by the bulb.

Also, your java ferns grew because they are an easy plant to grow, and dont require such specific light condidions as say Eustralis Stellata.
Also, a member of this forum by the name of shalu has a 55g that used to have a 3000K bulb on it and from the look of it he had great results.
He also has a 10g shrimp tank with 2 2700k screw in compact fluorescents and that tank looks great.
View his lighting thread here you can get links to his other tanks from his sig.

This proves plants will grow under those lights. But they will take time to adjust to the different light, and some may die doing this.

And adamjh, Yes, that could be a new way to go. But kelvin is still good for describing the color of the bulb. This should be condidered being added to the bulbs specs though. Good idea man.


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## adamjh (Sep 2, 2005)

Lorenceo said:


> And adamjh, Yes, that could be a new way to go. But kelvin is still good for describing the color of the bulb. This should be condidered being added to the bulbs specs though. Good idea man.


It's nice to know that someone out there can think I have some good ideas! Thanks!

By the way, I think New Zealand must have some of the most beautiful landscapes I have ever seen. I was in Auckland in 1999 and can't wait for the chance to visit again.


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## rey (May 17, 2005)

FWIW my current fave combo is 10K halide (daytime) with 50/50 fluorescents (evening). The 50/50s really bring out the green - I love them! Plants are happy enough...


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## malkore (Nov 3, 2003)

Lorenceo,
I'll agree that color temp is determined by spectrum.
But I won't agree that color temp is a good indicator of spectrum.

By your own words, some 18,000K bulbs are great plant tubes, and have a crisp whiteness to them...but these 'should' be very blue and 'only' suitable for saltwater tanks.

Honestly, I think the average, or even advanced hobbyist, still doesn't fully understand spectrum/lighting.
I mean how many times have you been told "actinic is useless for plants, it causes algae, blah blah blah", and now you have people stating how replacing their 10,000K with a 50/50 gave them better growth, specifically bushier growth?

We're still learning...and that's why friendly debates like what we're having are good...they only further our understanding.


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## DarkCobra (Jun 22, 2004)

malkore said:


> I'll agree that color temp is determined by spectrum.
> But I won't agree that color temp is a good indicator of spectrum.


Color temperature works very well to describe the color of a light where the light produced is a direct result of heat. The spectra produced is very smooth. Candle flames, incandescent lights, the sun, etc. are all characterised very well by color temperature.

Fluorescent lights are trickier, because they don't produce light via heat, they produce it via ultraviolet stimulation of phosphors, which produce individual spectral peaks at any chosen frequency.

To calculate the color temperature of a fluorescent, you take the frequency of the spectral peaks produced, weight them by intensity, and average them. Then you map the average frequency to a temperature using a chart like this:










Even that is a simplification, but good enough for us.

Now if the fluorescent is designed to replicate a natural heat-based light source as most are, color temp describes the color fairly well. A fluorescent producing pure white* is 6500K as expected. Lower color temps are more red/yellow, higher temps are more blue.

But take a fluorescent with an unnatural spectra, and things get weird.

A pure green fluorescent is also 6500K. So is one that produces 50% pure red and 50% pure blue, which appears purple, but spectrally averages to green! And a common blacklight, though it also appears purple, is producing longwave UV instead of red/blue, and its color temp is 15000K or higher.

So actinics, UV, and plant grow lights are *special cases* where color temperature no longer is descriptive of the color that our eyes see. Aside from these, color temperature is fairly accurate for the majority of fluorescents.

*6500K is indeed considered to be pure white. If you send a pure white signal to a TV, it is expected to produce 6500K white, and all broadcasts, DVDs, etc. are calibrated to that standard. Same goes for computer monitors and digital photography.

Of course, your perception of white is "colored" by your experience, as Lorenceo pointed out. Reefers typically have very distorted perceptions.

I experienced this myself when I switched from 3000K lights to 5000K. At first, it looked incredibly blue. Later, I perceived it as pure white. Now, it looks a bit yellow..


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## Lorenceo (Jan 29, 2004)

malkore said:


> ...But I won't agree that color temp is a good indicator of spectrum.


I didn't say that, that would be undoing all that I've debated
I 100% agree with you on that.

I said power glo's are pink, I didn't mention their plant growing abilities, but yes. Plants will grow under them.
All plants will grow in the typical ranges form 5500k to 10,000k and some plants will grow in temps lower or higher than that. And others wont.

As for atinic bulbs, I have no idea. I've never used an atinic tube. I dont like the blue on plants. Looks wierd, would be like the sun turning bright blue:icon_eek:

We are indeed still learning. I for one have never used a powercompact tube over 18 watts.:redface: (the 36, 55 and 96w ones you guys get over there are very hard to come by here.(and expensive))

I will be taking a leap of faith (sort of) with my new tanks lights, 2 of the tubes (of 6, other 4 will be daylights) will be OSRAM 8000K tubes. My logic is that they are cheap Amano bulbs. Will see how this goes.


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## Lorenceo (Jan 29, 2004)

You ninja posted me DarkCobra!:red_mouth
Some good points there, But I dont like the look of that complex chart..:eek5:


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## DarkCobra (Jun 22, 2004)

Lorenceo said:


> Some good points there, But I dont like the look of that complex chart..:eek5:


I agree on the chart, and almost didn't post it. But if you extend the lines, you can easily see that the theoretical pure green, and pure red/blue fluorescents really are 6500K. Otherwise, I realized that would have sounded like a pretty ludicrous claim!

Go here if you really want to bake your brain.


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