Jump to content

10000K 6500K ????s


Recommended Posts

OK you probably have answered this question for many a newbie, but I could not find anything in my search attempts. How is K measured. Is more K better or is less K better. I was reading one lighting thread and the person was looking for a 10000K light and said something about the 5000K lamp being an algae factory. So how does this work? Should I be looking for More or Less K.



I currently have an Eclipse 12 with about 9 - 10 lbs of live rock and 2 inches of crushed coral. 1 Percula Clown, 4 Hermits and 3 astrea snails. I had the bulb that came with the system, but recently switched to a 2 colored bulb (actinic blue and daylight) The LFS I bought it from said it was a better light but it seems dimmer.

Link to comment

K refers to Kelvin, a unit for measuring temperature.


The values for bulbs refer to the color's temperature, in degrees Kelvin. A low value is a cooler temperature, a high value is a warmer temperature. Whle it may seem conter-intuitive at first, the red end of the spectrum is the cool end, and the blue end is hot. Think of it from the perspective of how hot you have to heat something to make that color.


5000K ends up being a very cool color for aquariums. High in the yellow portion of the spectrum. Tropical natural sunslight is said to be about 6500K, at the water's surface. But water filters out the low end of the spectrum. So as you go deeper, the color gets hotter and hotter (although the intensity goes down). A 10000K bulb is said to simulate the color of light slightly underwater, and 20000K quite a bit more (for some reason, 10m and 20m come to mind, but I could be way off base there).


Ass long as you get more than 6500K, the value doesn't really matter.... it really coems down to perosnal preference. Do you like the yellower, softer look, or a more crisp blue/white look? That's really the difference between 5000K and 10000K.


Sometimes actinic bulbs will be refered to as 7100K, but don't get confused by that into thinking that 10000K bulbs are even bluer. The white/daylight bulbs, be they 5000, 6500, 10000, or 20000, have colors all over the spectrum, and the color temperature of the bulb is essentially determined by the summation of the colors. Really, it indicates where the main color is being produced. With actinic bulbs, all of the color is produced in the blue portion of the spectrum, which is in the low 7000's on the Kelvin scale. You could, technically, have a white 7100K bulb by adding color output both above and below the blue spike, but that is usually not done, jsut to avoid marketting confusion.


Hope that helps.

Link to comment

Great information. You are the first person that has explained it in a way that made sense (LFS couldnt really tell me). Thanks

Link to comment

Right! One thing though...


Color temp is the light put out by something when it's heated to that particular temperature (I forgot what the particular something is). As temp goes up, it gets less yellow/red and more white. At 10000K, it starts to look a bit blue and you can definitely see blue at 20000K.


Actinic bulbs have an infinite color temperature. I don't know why the one bulb is named "7100K Blue" but they're smoking crack.


* Coralife "100% Actinic 03 Blue 7100 K" - This lamp seems very similar to the Philips actinic 03 in spectral output and color (I did not test both _of_the_same_wattage_ side by side). The most significant difference between these lamps was the presence of a very weak red-orange line near 610 nm in the spectrum of the Philips lamp. This line was not present in the spectrum of the Coralife lamp. This line accounts for only a fraction of 1 percent of the output of the Philips lamp.  

I don't know how Coralife thinks the color temperature is 7100 Kelvin, or if 7100 K is just part of the name of the lamp and nothing to do with color temperature. This lamp is much more blue than infinite color temperature.  Since this lamp is so similar to the Philips Actinic 03, get whichever costs less.


Here's a great page on Color and Spectrum for flourescent lights. It's not aquarium specific, but a lot of the bulbs are covered. General color temp stuff is at the top; aquarium bulbs start about halfway down the page. It's written with Normal Output flourescents in mind, but the phosphors will be similar if not the same for the equivalent PC bulb. The quote from above is out of this page.

Colors and Spectral Characteristics of Flourescent Lamps



Link to comment

tungsten-electrically charged


i think the 7100K blue is the infamous 'blue bulb'. i equate uri's as 'true actinics' and everything else as wannabes. uri doesn't even give a rating of kelvin for the actinics (it maybe be that the rating process is inapplicable, i dunno ??? ).

Link to comment

Color temp is N/A for blue bulbs. I don't think one actinic/blue tube is really any better or worse than the next--pic the one that is most appealing you.



Link to comment

I wish bulbs went by candlepower rather than wattage. Wattage varies so much as to actual light produced by the various bulbs. IMO Candlepower would be a much more accurate way of judging the usefullness of reef lighting.

Link to comment

If you are interested in candlepower, you could ask the manufactuers for the intensity ratings, in lumens... They were more than happy to supply them for me when I was looking at up-grading my lights... :) Unfortunately, I through away the ratings... I can tell you that on average PCs are 2-3 times more powerful in terms of lumens than are thier NO counterparts... Thus, a 30W PC is about 2.5x as powerful as a 30W of NO.... Hope this helps you out. But don't be afraid to send the manufactuers a couple of e-mails... CoralSeaLife was probably the most responsive and most helpful.

Link to comment


This topic is now archived and is closed to further replies.

  • Recommended Discussions

  • Create New...