# Lamp temp question



## mcmasteri (Jun 4, 2006)

Hey everyone

With my new tank im going to use a MH and it comes standerd with a 10K lamp and im wondering if this lamp will be ok? for my plants .. im setting my tank up on monday . ill be using 2x 18watt pc's (6.5k) as well

thanks for any help


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## BryceM (Nov 6, 2005)

There are quite a few people that prefer 10,000K lights. Anything between 5,000 and 10,000 is usually ok. 5,000 is pretty yellow while 10,000 is white, even perhaps slightly blue.


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## Newt (Apr 1, 2004)

Lighting for a planted tank should not be chosen on color temp alone. It is true that 'full spectrum' bulbs are referred to as bulbs between 5000 Kelvin (K) and 6500 K and are best for planted tanks. Yet this does not indicate what type of light (wavelength in nanometers) the bulb is actually emitting. If you want both good leaf development/growth (blue light) and stem elongation (red light), you need light in both the blue and red spectra for photosynthesis.

Beyond choosing lighting that is optimal for photosynthesis, as above, you should choose lighting with the color temperature that best suits the aesthetic goals of your tank. So, don't obsess about color temperature beyond how you want your tank to look. From a color temperature standpoint, blue-colored light will enhance blues in your fish. Green-colored light will make the tank look bright to humans and enhance the green color of your plants. Red-colored light will enhance the reds in your fish, and any red plants.

BTW, 5000K is actually a white light and 10,000K is blue.


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## BryceM (Nov 6, 2005)

Newt,

Could you provide a reference regarding the red & blue spectra as they relate to plant growth, elongation, leaf growth, etc? If true, this is the first time I've seen it stated as such. It would make an interesting read and help to answer many questions that people have posed here.

The long answer is that there are many qualities and characteristics of bulbs that one can look at when comparing lighting. In fact, almost everything you see on the subject on a hobby forum will be a gross over-simplification of a topic that can consume volumes. The short answer is that most 10,000K bulbs will work just fine. The visual effect that it produces is best observed by the individual - not everyone likes the same look.

In my tanks, 5,000K bulbs make everything look pretty yellow. 10,000K lights make it look stark white or even a little bluish. YMMV of course.


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## mcmasteri (Jun 4, 2006)

my 10k lamps are pretty yellow  erm i have 70watt mh's with 5.2k and there inst much differance lol


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## Newt (Apr 1, 2004)

I use a mix of lights and one of them is a 5000K CF bulb and the color is white. The labeling of bulbs with the kelvin scale is not an exact science; especially when marketing is involved.









Below are a couple of jpgs showing where/how plants use light in the visible spectrum.


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## joephys (May 9, 2006)

Those charts are nice, but where do they come from? I have seen charts that are similar, but have higher peaks in the reds than the blues.

My 5000K bulb is white, but does look more yellow when compared to my 6700K bulb. Most of the 10,000K bulbs look white to me too, but bluish when compared to a 6700K. Therefor, I think its really subjective as to what color the light is.


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## erik Loza (Feb 6, 2006)

To all involved in this thread, please be aware that the mfrs' advertised color-temp output is subjective and there is a big difference between MH's and fluorescents in terms of how they would look on your tank. 

The Hit-Lite 10K HQI's I tried were too blue for my taste, yet my generic Chinese 10K PC's are actually quite nice. I use these 10K lamps in my PC fixtures and the ADA 8K HQI's (the closest I have seen to daylight color rendition in any halide lamp) in my MH's. You might consider them. Good luck.


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## ruki (Jul 4, 2006)

Mathematically, the Kelvins color assigned to a bulb is something of an average of the individual colors of a bulb. The same average value can be produced by many different samples sets of individual phosphor produced colors.



erik Loza said:


> To all involved in this thread, please be aware that the mfrs' advertised color-temp output is subjective and there is a big difference between MH's and fluorescents in terms of how they would look on your tank.


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## Newt (Apr 1, 2004)

ruki said:


> Mathematically, the Kelvins color assigned to a bulb is something of an average of the individual colors of a bulb. The same average value can be produced by many different samples sets of individual phosphor produced colors.


That's not what he is refering to. The kelvin color designation of a particular bulb is not always true to the black body locus line on a CIE Chromaticity map. This is why some 5000K bulbs look yellow and others white, especially when trying to compare a linear fluorescent with a CF or MH.









I once had a GE Chroma 50 (5000K linear fluorescent) and it was quite yellow. My Philips PLL950's (5000K CF) are white. also as another poster pointed out you may only see a difference when looking at two different bulbs at the same time. The GE 9325s look blue when alone but when compared to a 10000K bulb they appear pinkish. Go figure.

I wonder if the bulb's CRI has anything to do with it.

Guaiac_boy: I will try and find the reference to blue/red and their effects on plant growth. It may be from a Baench book or an author of another aquatic plant book.


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## ruki (Jul 4, 2006)

Newt said:


> That's not what he is refering to. The kelvin color designation of a particular bulb is not always true to the black body locus line on a CIE Chromaticity map. This is why some 5000K bulbs look yellow and others white, especially when trying to compare a linear fluorescent with a CF or MH


Perhaps this is due to the higher temperature of the light emitter behaving more like a blackbody than a cooler tube surface.


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## Newt (Apr 1, 2004)

guaiac_boy said:


> Newt,
> 
> Could you provide a reference regarding the red & blue spectra as they relate to plant growth, elongation, leaf growth, etc? If true, this is the first time I've seen it stated as such. It would make an interesting read and help to answer many questions that people have posed here.


My memory is not what it used to be................that's probably true for most of us. I took a look at the aquatic plants books and general aquarium books I have and didn't find anything as specific as what you want. What you want can be found online (well, what can't these days - duh). There is extensive plant literature on the relative effects of red, far red, and blue light on plant physiology. I think the Journal of Plant Physiology was the source of understanding the effects of blue and red spectra. Anyway, search the journals with key phrases. Use words like "phytochrome" "blue light" "red light" "leaf development" "far red" etc. You'll find enough reading to keep you busy for a long, long time.


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## BryceM (Nov 6, 2005)

Well, OK.

The great thing about the internet - all of the information is there.
The bad thing about the internet - some of the info is useful, most is not, sorting it all out takes too long. Maybe some other time.

Thanks for looking around for the reference though.


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## Left C (Jun 14, 2005)

Here's an eight year old article by Karen Randall that has some information about how red and blue light affects aquatic plants. It might help some. I tried to find something better. She said, "... I did say that blue light promotes shorter, bushier growth, while red light promotes taller, lankier growth. This wasn't an original statement on my part though, it's pretty well documented in horticultural literature..." She didn't mention where her info came from though. Light and Node Distance


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## BryceM (Nov 6, 2005)

In anyone is interested in this topic, I'd definatley read Karen's response carefully. She states, much more clearly than I could have, that this claim has not been verified or substantiated to any practical degree in aquarium plants.


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## ruki (Jul 4, 2006)

Left C said:


> blue light promotes shorter, bushier growth, while red light promotes taller, lankier growth.


Also, red lights promote blooming.

This is standard information from many, many greenhouse and hydroponics sources. They use the orange-red sodium lights mixed with halides.

Plants are plants, whether grown in soil, hydrocultre or submersed.


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## TWood (Dec 9, 2004)

All metal halide lights are not the same. Go HERE to search on various lamp/ballast combinations and see the spectral distribution chart.

Other than the 250W Iwasaki 6500K lamp, pretty much all the other lamps have almost all their PAR in a single spike at the 420nm spectrum. Probably because the reef trade is driving the technology. Some have more light in other parts of the spectrum. (EDIT: I haven't found even one with a spike up at the 640nm range.) There is an astonishing variation in the actual amount of PAR between lamps of the same wattage.


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## ruki (Jul 4, 2006)

You make me chuckle a bit. I wasn't talking about aquarium bulbs. I was talking about greenhouse/hydro bulbs Discount Hydroponics - Light Bulbs

Note that these would only be appropriate for indoor ponds because of their size.


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