Hi,

The relationship between lux and kelvin isn't very crystal clear. Lux is a measure of lumens per square meter. Lumens is the measure of intensity at a wavelength of ~550-600 nm (or green).

Kelvin colour is not really related to the lux. Let's suppose that an MH only produces three spikes of light - one at green, blue and yellow. It is fairly common for MH and fluorescents to do this due to the nature of the technology. If the blue spike moves to the violet...the kevlin increases...but the intensity stays roughly the same. The kevlin increases because the averaged wavelength of the light output is shorter -- which means a higher kelvin light. In other words...the light output has shifted to a blue tone. The green spike is what determines the lux intensity and the green spike stayed the same in both cases.

As for why the water is blue. This has to do with many things. This includes the reflection for the sky and blue-green algae in the water. But, RO/DI water is blue too ...this is actually a chemical property. Water is only semi-transparent at visible light wavelenghts. Its semi-transparency gets worse with longer wavelengths. So, long wavelengths get absorbed faster than short wavelengths in water. Hence, the blue light, which have shorter wavelengths, go through the water deeper than red lights. A similar argument can be made for why the sky is blue.

Hope that helps.

- Victor.

LOL, what a thread.....

Anyway...pic as requested...this probably doesn't offer much, I can get different pics with different lighting and different camera settings...



http://members.shaw.ca/bhadford1/BTAOct8.jpg

Hi,

Okay...let me try this again since I totally missed the entire question...

Does intensity change with depth (in nature) ? Yes. At deeper and deeper water depths, more and more red light is filter. The yellow/green is not as filtered as red. And the blue/violet is the least filtered. To answer the third question, yes the blue is of lesser intensity; however, the filtering effects of 10m of water is not too bad for blue light. I would say that 75% of the blue still makes it through 10m of water. Red/Yellow and green are non-existant. In this example, depth does change the kelvin of the lighting -- deeper equals higher kelvin and lower intensity (PAR for example). For MH and NOs, it is not quite the same story because the light spectrum is in bands while sunlight is full spectrum.

- Victor.

Thanks for that Victor. That to me leads to an inescapable conclusion, (which was confirmed by more reading). That conclusion is that we only need to supply FULL SPECTRUM lighting for the biological health of the creatures we keep. This needs to be of adequate intensity. Full spectrum (5500K) has all the wavelengths, and is all the creatures need. It seems to me that all the actinic supplementation we do is for our own benefit, as we have eyes and corals do not. There might be a downside to just having high intensity full spectrum lights. That is it seems nuisance algaes do better when all wavelengths are present. That however, is just my own obsevation, and may be incorrect. :D
Actually when I look back to very early in this thread, I am only confirming what Steve has already said. :D

Quote from Steve Tyree's Book RBSC

A light field that was primarily blue would mirror what the corals experience in clean ocean waters at depths from 10 meters and deeper. At depths from 5 to 10 meters, the light is mostly blue/green.

The zooxanthellae within these corals all contain caroteniods which only absorb blue light and of course also contain the chlorophyll's that absorb much more blue light then red.

And one more.

The study also determined that low levels of blue light can acheive rates of light-saturated photosynthesis(peak operation) that are equivalent to those reached by corals grown in full sunlight.

Of course you are indubitably right, but the point I am making is that FULL SPECTRUM light contains that blue light it is just that the rest of the spectrum is NOT being filtered out by the water. Thus the conclusion I have come to is that blue supplementation is not required for the health of the corals. It just pleases our eyes. :D

I think that Jamie is saying that the more blue you pump into your tank the better. But to get a pleasing color to your eye you have to add other colors of the spectrum. Blue is deffinatly most needed for skelital growth and a healthy zoz population.... :lol:

Here, read this as opposed to getting information written for hobbyists:

http://www.cbl.cees.edu/~mattia/SMPr...ackground.html

Bob,
What I'm reading is that the coral is using the blue light. There for if your supplement blue light the coral is using it. I don't think it gets any clearer. If I'm going to put a bulb over my reef I want it to have the spectrum that is most usable by the animals I keep. And by this statement it's blue light.

The study also determined that low levels of blue light can acheive rates of light-saturated photosynthesis(peak operation) that are equivalent to those reached by corals grown in full sunlight.

Hi,

Ah...its the blue light special theory. :D

But seriously, I think its a pretty nice theory. Only problem is....how do you know your lights are the right blue and violet ? If you have compared the spectrum of brand X MH with the nature's spectrum of light at 15m, then you'll realize...I don't even think they are similar at all. The banding effects you get from MH cause all sorts of problems and it leaves certain wavelength with very low blue-violet light. If the Zoox happen to like a specific wavelength that your lamps have a null ...opps.

Blue light special works pretty well for some corals...and not so well for other corals. Anybody heard of a bunch of reefers say that their Toadstool's colours are beyond belief when they switch from Iwasaki to Radiums ? In the same breath...you hear another reefer saying that his blue tip acro is more happy in is Radiums than his Iwasaki. Yah..I know its a extreme example...but seriousily, some corals are affect by the blue light special while others are not. So why is this ?

My personal theory is that corals will change to what every conditions are present in the tank. It is natural for organisms to do this since it is written in to their DNA. Some corals are able to adapt and survive, while others die because they can not. When we apply blue light to a purple monster, it changes to something we find rather pleasing. There are many types of pigments and zoox on a coral. My theory is that certain light bands cause certain pigments and zooz to dominate. So, blue light causes a group of Zoozs to dominate and it is what causes the purpleness in the purple monster. Green light will cause another group to dominate and so on. So...does this mean certain groups of Zoox (or colour) mean better health. I don't know, but I am leaning towards it does not. If the same number of energy producing Zoox that are in the brown Purple monster and the "true" purple monster, then both corals should be just as happy. The only difference is colour...like our skin colour -- okay maybe that's going a little too far, but I think you get the idea.

So those are my thoughts...what are you thoughts on this subject ?

- Victor.