# 6,700K vs 10,000K in planted tanks



## OVT

It caught my attention that a lot of people are using 10,000K lights in their planted tanks.
Let's say we take 2 bulbs from the same manufacturer (Coralife), one 6,700K and another 10,000K (I could only find their respective spectrum info on the packaging, not on the web).

Visual appearance of the tank aside, any significant effect on plans one vs the other?

(Sorry if this subject has already been beaten to death ..)


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## jrman83

I think is more personal pref than anything. I just recently switched to a mixture on my lights because it makes all the colors in my plants and fish really pop. I did however, see a slight difference (higher) in PAR testing of my lights using 10000k bulbs. Haven't noticed any growth differences.


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## BBradbury

*Your Bulb Question*

Good morning OVT...

I've used 6500 K bulbs in my planted tanks for several years. Natural daylight registers 5500 K, so I use bulbs that come closest to that. The light blue color hue mimics natural light conditions.

I'm not an authority on lighting, but IMO a bulb with a K rating close to 6500 would be best.

B


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## kevmo911

No, there will be no difference in plant growth between a 6500 and 10k bulb from the same manufacturer. People like mixing the 6500 and 10k bulbs for the color.


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## jacob.morgan78

You need to consider how the K rating changes as the light passes through the water. It may be 5500K at the surface but when that passes through the water it changes significantly the deeper you go.


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## redfishsc

jacob.morgan78 said:


> You need to consider how the K rating changes as the light passes through the water. It may be 5500K at the surface but when that passes through the water it changes significantly the deeper you go.


Color penetration and attenuation is completely irrelevant in an aquarium. 

You see nearly no measurable loss in color in an aquarium in terms of water depth. 


You need to get into the 15-30 foot deep mark before you see the first colors of light (reds) being attenuated.


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## AirstoND

Just noting the spectra on boxes, 10K have a broader and higher intensity blue spectra(low wavelength), good for bottom dwelling corral and invertebrate. Aquatic plants just get more types of algea growing on them from 10K.

I would recommend raising a 10K light more than a 6500K bulb for a freshwater planted tank.

6500K have narrow high intensity spectra specific to plant photosynthesis, than minimizes different types of cyanobacteria growth found when using broader, low wavelength spectra(10K bulb)


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## jacob.morgan78

redfishsc said:


> Color penetration and attenuation is completely irrelevant in an aquarium.
> 
> You see nearly no measurable loss in color in an aquarium in terms of water depth.
> 
> 
> You need to get into the 15-30 foot deep mark before you see the first colors of light (reds) being attenuated.


I should have clarified that I was not talking about an aquarium but in nature where the light does pass through that much water.


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## redfishsc

jacob.morgan78 said:


> I should have clarified that I was not talking about an aquarium but in nature where the light does pass through that much water.


My apologies then . So you were suggesting that the blue light is more effective for plants since the red tends to get attenuated in natural environments? Most of our plants probably come from waters much shallower than the 15-20 feet that attenuates the red... but then again very few of our plants come from waters that get sun blasted all day------ most are shaded by trees, other larger plants, floating plants, stained water, etc. 


I wonder just what spectrum of light does penetrate into the various water types that our plants come from. I'd imagine that water stained with lots of tannins would filter our the red light quicker than we might expect.


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## jacob.morgan78

redfishsc said:


> My apologies then . So you were suggesting that the blue light is more effective for plants since the red tends to get attenuated in natural environments? Most of our plants probably come from waters much shallower than the 15-20 feet that attenuates the red... but then again very few of our plants come from waters that get sun blasted all day------ most are shaded by trees, other larger plants, floating plants, stained water, etc.
> 
> 
> I wonder just what spectrum of light does penetrate into the various water types that our plants come from. I'd imagine that water stained with lots of tannins would filter our the red light quicker than we might expect.


This is where this differs a lot from the concerns of my reef tank. You wouldn't need to worry about shade from trees on the reef! 

I would LOVE to see some data or studies done on just what spectrum and PAR are available in the plants natural environment. That would be some valuabe information. It has to be out there somewhere I would assume.


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## 2in10

Generally speaking 6500K bulbs will give a yellowish tint and the 10000 bulbs a whitish tint. The bulb at the front of the tank will have the greatest effect on what color the tank looks. Growth will be the same with either bulb or a mix of the two bulbs.


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## OVT

Thank you all for your insights. I think the proof is in the results: I will pop a 10,000K in my 4x36" fixture over my grow-out tank and see what happens. Learning, experimenting, and sharing keep me in this hobby.
Cheers.


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## zergling

2in10 said:


> Generally speaking 6500K bulbs will give a yellowish tint and the 10000 bulbs a whitish tint. The bulb at the front of the tank will have the greatest effect on what color the tank looks. Growth will be the same with either bulb or a mix of the two bulbs.


This.



OVT said:


> Thank you all for your insights. I think the proof is in the results: I will pop a 10,000K in my 4x36" fixture over my grow-out tank and see what happens. Learning, experimenting, and sharing keep me in this hobby.
> Cheers.


Reef folks have done soooo much testing with bulbs, much more than us freshwater planted tanks folks (probably) will ever do. I myself have experimented around with many different bulbs that were made for reef tanks to make certain colors pop. At the end of the day, it's all about color preference. 

Some bulbs (the higher quality ones) do output more PAR, but that's not that big of a deal for our plants, as folks have tested that plants can grow at lighting as low as 40 PAR. Much unlike reef folks where SPS corals are ideally grown under 500-600+ PAR.

For us planted tank folks, just pick the bulb combination that gives off the color that you like -- then spend the rest of time keeping CO2 and nutrient levels enough to prevent deficiency and the consequent algae bloom.

For those that wonder, I've played with ATI AquaBlue (currently use this too), ATI PurplePlus, ATI Blue Plus, ATI Actinic, UVL Red Sun, KZ Fiji Purple, UVL Super Actinic, and probably a few more that I can't remember at the moment.

"Recent" Pic. This is using Giesemann Midday, ATI AquaBlue, Giesemann Aqua Flora, and GE 6500K









Same tank, same fixture, 4 years ago. IIRC, this pic was when I was using 2 x UVL AquaSun, ATI AquaBlue, some pinkish bulb (KZ something, I think).


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## galabar

This uses 2 x 10,000 K Coralife bulbes (in Coralife fixture):

http://www.plantedtank.net/forums/tank-journals-photo-album/157203-my-40-gallon-breeder.html

I used these because that is what I had and I didn't want to pay big bucks for new 6500 K 96 watt PC bulbs. 

When these bulbs die, I'll probably move over to LEDs.


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