# Coralife colormax K rating?



## ShrimpieLove (Apr 26, 2010)

Hi everyone! 
I have a bulb that Ive been using in My light fixture... I cant seem to find any info about it though as to what the Kelvin is for this bulb? Its a Coralife Colormax mini compact flourescent 10 watt freshwater bulb...i was wondering why a bulb that is specifically for aquariums wouldnt have the K listed on it... 
Really im curious if this bulb is doing anything for my plants at all... I have other bulbs on the tank so the plants closer to them are doing well but the plants under this bulb arent doing as good... Its a nice color light but maybe someone has info about if its any good for the plants at all?


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## wtac (Mar 17, 2006)

The given spectral plot is fine for plants but you have answered your own Q .

The bulb isn't strong enough to emit sufficient light to the lower level plants. It's primarily due to the configuration of the bulb and reflector in the lighting system. Drawing from the SW reef hobby, it's not an efficient "style" of lighting. Aside form reflectors to divert the emitted light down to the aquarium, the bulb shape itself is it's Achilles Heel. As light is emitted, a significant amount hits the adjacent tube (restrike) and very little is reflected off to the intended target area.

CFLs are essentially FLs which are categorized as diffuse source light emmission. Just that the FL tube is reconfigured in a broad attempt to make it a point source light emision like MHs.

HTH, JMHO/2C


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## AquariAM (Jan 28, 2010)

wtac said:


> The Diagram of light with different colors is fine for plants but you have answered your own Q .
> 
> compact fluorescents that screw in are essentially fluorescents which are categorized as diffuse source light emmission. Just that the fluorescent tube is reconfigured in a broad attempt to make it a point source light emission like metal halides.
> 
> HTH, JMHO/2C


^ De acronymed for the new


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## bae (May 11, 2007)

Color temperature ratings are really kind of a kluge when applied to fluorescents. The concept is that if you have a chunk of matter, and you heat it, it glows. First in infra-red, then as it gets hotter in red, orange, up the spectrum to blue-white, as perceived by our eyes. This is called black body radiation, a black body being the perfect absorber and radiator of light, made out of ideal matter rather than the real stuff.

Incandescent lights work by heating a piece of tungsten wire to a high temperature by using it as an electrical resistor. It gets heated to a specific temperature and emits light at a specific wavelength, somewhere around 2700K, more or less -- it's actually a bit of a range because this is real matter, not ideal matter. Halogen bulbs work on teh same principle except there's a halogen gas in the bulb that makes it possible to heat the wire to a higher temperature and a whiter (less red) light without evaporating the tungsten too fast. Standard CFLs try to emulate the color of incandescents and are rated at 2700K.

Fluorescent tubes work on a different principle. An electric arc excites atoms in the tube to produce UV light, which strikes a coating on the inside of the tube and causes it to fluoresce. The color of the emitted light depends on the chemical composition of this phosphor coating. Phosphors can be mixed to make a coating that emits different patterns of wavelength. The graph on your packaging shows the wavelengths in which most of the light is emitted. Black body radiation isn't spiky like that -- it's a smooth curve over a range of wavelengths. Phosphors can be mixed to emulate various black body color temperatures, but not all tubes contain that kind of mix. Grow-lites, for example, emit mostly in blue and red, to match the absorption spectrum of chlorophyll.

There are other ways to describe light emission. One is lumens, which indicates how bright the light appears to the human eye, which is most sensitive to wavelengths in the green to yellow range. Another is PAR (photosynthetically active radiation) which indicates how much of the light is in chlorophyll's absorption spectrum. This isn't necessarily the ideal for plants, which have other pigments that absorb other wavelengths and pass the energy on to the photosynthetic chain. These mechanisms are most developed in plants that don't get much unfiltered sunlight -- shade plants and underwater plants.

At any rate, color temperature in fluorescents is basically a measure of how reddish or bluish the light will appear to your eye -- low numbers are redder and high numbers are bluer. 'Warm white' is fairly reddish. It popular for kitchens and bathrooms because it makes food look more appetizing and skin look more healthy. 'Cool white' is technically in the greenish range, although it doesn't look particularly green to the human eye. Plants will look greener under it, and it has a high lumen rating because it's a fair match to the greatest sensitivity of the human eye. This happens to be a particularly inexpensive phosphor formula, and cool whites have long been the standard for factories and warehouses. 'Sunlight' is a mix of phosphors that emulate sunlight, like your tube. 'Daylight' is fairly blue -- like light from the sky away from the sun, i.e. 'north window light'. All of these will grow plants, so what you pick can depend mostly on what you like the looks of.


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