# 6500k vs 10000k lights



## DiscusLoverJeff

From my experience, the 10k have a slightly bluer tint and make your fish colors come out more. 

The 6500k have a slightly pinkish hue based on the spectrum scales. 

Also, different manufactures will have a different tints to their bulbs as well. People seem to also like the look of the same bulbs in the T5 fixture over the CF fixtures.


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## jrman83

But will all else be the same?


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## DiscusLoverJeff

They say that the lower the Kelvins, the better for your plants. I have 6500k in my 95g tank and my plants are doing well. If you have a 4-bulb fixture, you can mix to get a different effect. The 6500k bulbs are the closest to natural sun light. Some people would disagree, but I think for plants and growth rate, I prefer 6500k. As far as algae growth, I see some in my tank at times, but my cleaning crew makes a quick meal of it so I rarely have to clean anything like the glass. 

As far as time, I have mine (4 bulb fixture) set to come on in two stages as to not spoke my discus. I run 2 lights for the first hour then 4 for a total of 8 hours per day and then close the night for 1 hour with 2. So a total of 10 hours of light.


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## BBradbury

*Your Lighting ?*

_Hello jrman. The information you have is essentially correct. The 6,500 K (Kelvin) tubes most closely resemble natural daylight. These are recommended for most planted tanks. However, any tube in the 5,500 to 6,700 K range will work for most plants requiring low to moderate lighting. _

_The Kelvin system is based on the color of the tube. To me, 6,500s appear a light blue. The 10,000s are a different color tint, possibly a pink. You can Google "Kelvin" and get the skinny on the lighting._

_BBradbury _


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## Hoppy

I think you are asking if there is any difference in plant growth with the two bulbs. I haven't seen any tests on that, but I'm willing to bet if you have the same PAR with the two bulbs, the plants will grow the same, as will the algae.


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## jrman83

Hoppy said:


> I think you are asking if there is any difference in plant growth with the two bulbs. I haven't seen any tests on that, but I'm willing to bet if you have the same PAR with the two bulbs, the plants will grow the same, as will the algae.


That is more of what I was asking, yes. Didn't think about PAR. 

Have you tested to see if there are differences between kelvin ratings with regards to PAR on a light fixture.


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## Hoppy

jrman83 said:


> That is more of what I was asking, yes. Didn't think about PAR.
> 
> Have you tested to see if there are differences between kelvin ratings with regards to PAR on a light fixture.


No, I haven't, nor have I seen any data from anyone else doing that. There is still an overwhelming amount of information we could seek, when it comes to lighting.


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## redfishsc

There is some data available. It's a few years old, and some of the bulbs are no longer made, but it suggests to me that the exact color temp isn't a big deal. Bulb quality, however, is HUGE.

"Grim Reefer" over on Reef Central found that the ATI Blue Plus (a pure blue 460nm) puts out MORE PAR than some white bulbs (such as Current USA 10K). 

Here is his data. Notice the ATI Blue Plus 460nm whips the Current USA 10K. 

The 10,000K UVL Aquasun puts out nearly the exact same as the 6500K GE Daylight. 

From this post:
http://www.reefcentral.com/forums/showpost.php?p=8051316&postcount=15


> ATI
> 
> Sun Pro 357
> Aquablue 336
> Blue Plus 311
> Actinic 137
> 
> D&D/Giesemann
> 
> Midday 325
> Aquablue 324
> Actinic Plus 264
> Pure Actinic 157
> 
> UVL
> 
> Aqua sun 345
> Actinic White 293
> Super Actinic 210
> 
> AquaZ
> 
> Sun Pro 285
> Ocean Pro 323
> Blue Pro 266
> 
> Helios
> 
> Daylight 309
> Super Blue 225
> 
> Current Sun Paq
> 
> Daylight 10K 272
> Blue 252
> 
> GE Daylight 340


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## jrman83

Thanks for the info.

I was also looking at the daily plant profiles and saw one plant that had a few pictures where the color variance in the plant went from a near yellow to a very dark green. The comments were that the lighter colored plants were from bulbs in the 6200-6500k range. So it makes me wonder....does the 10000k light offer a better color response out of the plants? Is there a proven kelvin range that is better for greens/reds/etc in your plants?


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## xjia

10k bulb will have higher blue spectrum- more towards bluwish colour. 6k more towards green spectrum...white colour.


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## jrman83

xjia said:


> 10k bulb will have higher blue spectrum- more towards bluwish colour. 6k more towards green spectrum...white colour.


I've seen how they look in my tank, but some things I'm reading sounds like there could be slightly different responses from the plants. Does a light closer to blue or pink, or other, in color make a difference in plant growth, color, or whatever else the light effects? Does photosynthesis occur a different way based on the spectrum of light a plant gets? Not major changes, but maybe enough to see different growth rates or color response from the plant. If it does, what visual differences would we actually see? Realizing the avg low-light plant won't matter maybe. 

It was all just something I was pondering.


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## jasonh

The kelvin rating is just a way for us to talk about how the bulb "looks." The real difference is in the actual spectral response of the lamp. If the spectral curves of the 2 lamps are similar and PAR is similar, I'd suspect you would get similar results. I would also not be surprised to see certain plants doing better/worse under one bulb or the other (AFAIK, not all plants respond exactly the same to various wavelengths). 

Does it matter? Probably not.


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## trackhazard

jasonh said:


> The kelvin rating is just a way for us to talk about how the bulb "looks." The real difference is in the actual spectral response of the lamp. If the spectral curves of the 2 lamps are similar and PAR is similar, I'd suspect you would get similar results. I would also not be surprised to see certain plants doing better/worse under one bulb or the other (AFAIK, not all plants respond exactly the same to various wavelengths).
> 
> Does it matter? Probably not.


I agree with this.

Also, one company's 10K is not necessarily another company's 10K both in terms of look (Kelvin) and performance (PAR).

-Charlie


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## jrman83

It does matter if you have a particular plant that you have either shows more green or red, growth rates, under one bulb vs the other (if that data is out there - the original question) and you want that particluar effect out of your plant. Does it matter to the plant, no. But it does to me if I know that info to choose the lights I put in my fixtures.


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## jasonh

jrman83 said:


> It does matter if you have a particular plant that you have either shows more green or red, growth rates, under one bulb vs the other (if that data is out there - the original question) and you want that particluar effect out of your plant. Does it matter to the plant, no. But it does to me if I know that info to choose the lights I put in my fixtures.


If you're looking for something specific then that's another ballgame. In general terms though, as far as average growth rate on average plants, you probably won't see a lot of difference between the average 6500k bulb and the average 10k bulb. So to directly answer the first post in this thread - negligible.


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## BBradbury

*Gen'l Lighting Info.*

_jrman. Apologies if I misread your post. Thought I understood a little about tank lighting. From the other postings, apparently, I don't. I understand degrees Kelvin (K) is simply a measure of the color quality of the tube. Natural daylight measures 5,500 K. So, I figured a 6,500 K tube would come closest to natural daylight. If I can get that in a tube, then that's what I generally use. The 6,500 Ks I've found come in T8s or T12s._

_I've always used standard florescent light for my planted tanks and have plants that require moderate light. Don't know about you, but I have several tanks and am on a limited budget. The florescent tubes are very inexpensive, no more than $10 to $12.00 at the local Lowe's. _

_As far as intensity, the 10,000 K tube looks brighter, more intense to me than the 6,500 K. If that's the case, then the plants requiring moderate light would grow faster, but die off more quickly. I think the 6,500 K would be the better choice for a tank of moderate to low light plants._

_BBradbury _


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## prjct92eh2

jrman83 said:


> I've seen how they look in my tank, but some things I'm reading sounds like there could be slightly different responses from the plants. Does a light closer to blue or pink, or other, in color make a difference in plant growth, color, or whatever else the light effects? Does photosynthesis occur a different way based on the spectrum of light a plant gets? Not major changes, but maybe enough to see different growth rates or color response from the plant. If it does, what visual differences would we actually see? Realizing the avg low-light plant won't matter maybe.
> 
> It was all just something I was pondering.


I think you may be confusing the actual color of the plant with the perceived color by our eyes. What your eyes see is spectrums of color reflected by the plant. Since the bulbs put out different spectrums, what your see is different colors.


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## jrman83

Not really talking about what I see at all. Just was looking from the aspect of different responses from the plant from different kelvin or spectrum of light - nothing more. When it comes down to it I'm not too concerned about how the tank looks to my eyes with 6500k or 10000k, but more how the plants are doing from what I am using. 

I have CA fixtures on my 125g, all with 6500k bulbs. However, I have a set of 10000k bulbs and was wondering if one or the other causes different reactions from the plant. If the result is nill, then okay. Was just asking.


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## xenxes

Any update to this? How did the plants under 6500k and 10000k grow out?


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## jrman83

Wow, old thread.

I changed one of my tanks to 10000k, but haven't noticed much difference in plant response. Looks much different, but that is about it.

I did some PAR testing and the PAR readings were a little higher with the 10000k bulbs.


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## samamorgan

Nothing you do with visible color changes is going to change how the plant responds. The only thing that effects plant growth in regards to light is PUR. Kelvin tells us nothing about PAR/PUR/Spectrum, which are the only concerns when it comes to the health of the plant. The best possible plant bulb you can get looks HORRIBLE, a combination of pure blue and pure red, but the plants eat up that light like nothing else.


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## ktownhero

samamorgan said:


> Nothing you do with visible color changes is going to change how the plant responds. The only thing that effects plant growth in regards to light is PUR. Kelvin tells us nothing about PAR/PUR/Spectrum, which are the only concerns when it comes to the health of the plant. The best possible plant bulb you can get looks HORRIBLE, a combination of pure blue and pure red, but the plants eat up that light like nothing else.


Somebody should run a tank with a 5,000K pink, plant-grow bulb and a 20,000k actinic bulb and see what happens :icon_cool


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## gex23

Just to bump this up.

I have a poison dart frog vivarium, and will be using a recently purchased 6 x 39w ATI Sunpower Dimmable unit on it.

The plan is for 2 bulbs for the first 4 hours of the day (ramping up to 100% within the first hour), with the additional second channel of 4 bulbs for the middle part of the day, and working backwards to night.

However, i'm struggling to decide on a 'natural' light combination for the inhabitants (whom originate in heavily canopied rainforest in Panama).

I was thinking 1 x grolux pinkish tube with a 6500k tube initially, followed by a combination of 2 more 6500k and 2 x 8000k skywhite tubes?

Or is this complete rubbish?

Any thoughts or input would be appreciated.

Anthony.


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## mach_six

Try the Giesemann Aqua Flora T5 HO Lamps, their spectral graph peaks in the red and blue. I use it on my saltwater tank for macro algae, they were growing well until they were all eaten up.

http://www.giesemann.de/64,2,,.html


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## brainwavepc.com

I use three 6500k and one 10000k in my 4 bulb t5ho lamps and it makes the tank look better to the eye than all 6500k but growth hasnt changed. the tank looks more natural with a 10000k. more reddish color to the plants and fish than all 6500k


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## SMB

Does Giesemann make a 10K T5 HO bulb?

Also, and this may be a stupid question, but as a photographer, if you want to get an idea regarding how your tank would look at different Ks, why not take a RAW photo of your tank and use the White Balance slider in post processing to see different effects? This would only work I guess for one bulb type.


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## polska

*my 2 cents*

I had 2 6500k CF on my 20 gallon tank...maybe 60 or 75 watts (and the tank looked great) then I switched to a 2 foot long dual lamp T5 with a 10000k and a softwhite and after about 2 or 3 weeks I noticed very slow growth (compared to the 6500k bulbs) and a huge algae bloom of staghorn algae. I've since removed as much of the staghorn algae as possible and removed the T5 lamps and switched back to the 6500k bulbs and I haven't seen any new algae growth since. 

From my experience I probably won't use the 10000k lamp again.


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## Green_Flash

Anyone know where to find 8,000K T5 bulbs? Thought ADA made some, guess not.


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## xenxes

polska said:


> I had 2 6500k CF on my 20 gallon tank...maybe 60 or 75 watts (and the tank looked great) then I switched to a 2 foot long dual lamp T5 with a 10000k and a softwhite and after about 2 or 3 weeks I noticed very slow growth (compared to the 6500k bulbs) and a huge algae bloom of staghorn algae. I've since removed as much of the staghorn algae as possible and removed the T5 lamps and switched back to the 6500k bulbs and I haven't seen any new algae growth since.
> 
> From my experience I probably won't use the 10000k lamp again.


I think that's from your sudden increase in the amount of light (PAR), resulting in algae bloom outcompeting plants, nothing with the spectrum.

I'd like to see side-by-side pics of similar tanks with 6500k vs. 10k, 2x 6500k bulb & 2x 10k bulbs, 3x 1x, etc, rather than experiment myself lol.

*Nevermind found one


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