The truth about lighting

ScottT1980

ScottT1980

Well-Known Member
I thought I might start up another discussion here only because I know very little about the subject matter and I thought others could fill me in...

I have just recently changed my bulbs on my tank from a lower end kelvin spectrum strictly to 2 50/50s and 2 actinics and it got me thinking. I have read so much saying that Kelvin does not matter and that PAR perhaps does or doesn't matter but I have never seen any of the primary literature discussing such.

Have there been any studies looking at growth rates under different kelvin bulbs to back up what everyone says, that the kelvin rating of a bulb does not matter? If not, then how has this conclusion been drawn? And, as for intensity, any growth studies here?

Mojo, I know you gave me a little bit of info in chat last night but I wouldn't mind seeing it fleshed out a bit (not to put you on the spot by any means, I just remember talking with you about it very briefly).

Thanks
Scott T.
 
Maxx

Maxx

Well-Known Member
I would also check the library forum under lighting.
This the same thread that TG has linked up above. I inadvertantly irritated Sanjay Joshi and he wound up replying to the thread to correct my misconceptions. This is for pg 26 where he posts some links for his newer tests and theri results. Try about half way down, the first series of links don't work for some reason....
http://reefcentral.com/forums/showthread.php?s=&threadid=254667&perpage=25&pagenumber=26
Nick
 
Craig Manoukian

Craig Manoukian

Well-Known Member
On Saturday, Anthony Calfo made an interesting point. He believes that light supplies only up to 15% of the nutritional requirements of photosynthetic animals. The remainder of that requirement has to be made up of the proper foods. In other words it is better to underlight your tank than underfeed your corals.

My understanding is that the Kelvin rating equals the color and that the PAR is related the intensity or the ability of light to penetrate a certain depth. Metal Halide lighting can support a deeper tank with light than a Power Compact light, but they can both have the same color spectrum with a 10,000K bulb.

I hope this is correct as it has taken me quite some time to be able to put it in simple terms. If not, oh well, back to the drawing board. I knew I should have taken physics somewhere along the line.:columbo:

:) :D ;) :p :smirk: :cool:
 
ScottT1980

ScottT1980

Well-Known Member
Thanks guys, I have plenty of reading ahead of me and to be honest, the reason I posted was because of the other thread started by MPS. While I haven't gotten through all of the RC thread, I still have not seen any mention of a specific study.

So, Boomer says this:
Growth is a function of PAR/PUR or total irradiace, to include "food" and K plays almost no roll, if any at all. K is mostly a function of change in color, as observed by you, not that the coral has changed . It is our eyes playing tricks on us or in many cases the corals, by certain lighting, which produce a greater response of fluorescing substances.
Click to expand...

But, I still have not found the literature supporting such, and when I say literature, I mean real scientific studies. I am sure it is out there, I just haven't found it. Of course, finding any primary literature in this field is VERY difficult so it might not be there. If not, then I would be guarded about statements like this. Perhaps I can coax Boomer in here to set me straight (although he has probably answered this question ad nauseum before). :D

Take er easy
Scott T.
 
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ScottT1980

ScottT1980

Well-Known Member
I guess to restate, I have seen tons of data testing this bulb or that bulb but I have never seen data testing various bulbs and PARs on coral growth. Does that make sense? Again, I still ahvent gotten through the RC thread so perhaps I will find it there.

Perhaps the data only exists in plant/algae studies and the dogma has just carried over...

Take er easy
Scott T.
 
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ScottT1980

ScottT1980

Well-Known Member
Here is an interview I found on the web although Dana Riddle is not a name I recognize.

http://www.netpets.com/fish/fishnews/articles/riddlewalch.html

It is sort of a reiteration of what is previously been mentioned and she mentions that there is some research out there but I have yet to find it. I guess the fact of the matter is that while Kelvin and PAR are two separated entities, there is some correlation and as is intuitive, the higher the kelvin, then typically the lower the PAR (more or less anyway).
 
Witfull

Witfull

Well-Known Member
basically,,,corals dont care about the color of light, it is the intensity of the light. the K factor of bulbs is for a few reasons, one, pure visual appearance...what do we like to see..2, the higher K ratings grow less nuisance algaes- major plus!
now the K factor affects intensity, the higher the K factor to less instense the light is..there for you need it up the wattage to get growth from corals with higher K. example- a 175 6500k bulb will give the gorals good growth, but to get the same growth with a 10k you would need a 250 watt bulb, or a 400 watt 20k.
 
ScottT1980

ScottT1980

Well-Known Member
Thanks for the link Scott, I remember reading that a while back but had forgotten about it. And yes, actual data like that in the RC thread :D

One statement to note:
On the other hand, it is also very possible that some of the pigmentation that we see is due to too much light. Once a coral reaches P-max, more light actually lowers the rate of photosynthesis slightly. So a safer approach might be to look at lowering the light levels somewhat.
Click to expand...

So obviously, growth studies are a bit difficult as I would assume the P-max varies from coral to coral. I wonder if there are any P-max values out there for various corals? Also, isn't P-max measured by O2 respiration (its been a LONG time since undergrad botany)? I would think this would be difficult to assess with corals as I cannot think of an accurate way to asses oxygen respiration under water (calling all marine biologists, do you guys know?).

Just thinking out loud...I will do my own homework when I get a chance today.

I guess one glitch that keep running in my mind is that photosynthesis, at least in plants and only from what I recall, does have a higher efficacy at certain wavelenghts and from what I understand about kelvin changes, it is essentially a change in wavelength. Has this idea been refuted or is it not applicable to coral. Also, can anyone give me a nanometer reading for different kelvins (perhaps I could have it all confused).

Take er easy
Scott T.
 
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Scooterman

Scooterman

Active Member
Craig, in layman's terms, you hit it right on the head.
Please remember, these are some thoughts, I stand to be corrected.
I've studied light years ago, it's effects and absorption is one thing that can get tricky. There is so much information on lighting, that I myself haven't studied on that level but understand what is going on. I agree with Boomer and the PAR for aquarium use is very important, the higher PAR the deeper penetrating or radiation ability of light,. Now with that said, Kelvin, is light measured in temperature, this affects color. All matter either absorbs light or reflects it, white light holds ALL of the colors in the spectrum, black colors are just the opposite, pigmentation of matter will determine how much light is absorbed or reflected. First of all you have to reach corals, so PAR rating is that, intensity of the actual light spectrum being lumens. This ability to penetrate water is what we look for in PAR. I may be corrected on this point but Kelvin in my thoughts of light is varied in reef lighting because one, our viewing prospective & two some level I have to believe that corals absorb light differently at different Kelvin levels, no two are alike, no two are feed the same either. If your looking for best growth, from what I've read 6.5k range will cover all of your corals needs but looks yellowish or crappy in my opinion. This is one subject, I love to read about and at the same time tend to keep commits short, there is too much to cover without causing a major controversy.
 
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mojoreef

mojoreef

Just a reefer
Boy this one maybe a good one for me to watch,hehehe.
K is the tempature of the bulb. the temp will effect the color of the bulb to our eyes but also the wavelengths of color waves being generated. Corals zoox have the ability to absorb certain wavelengths directly (violet and Blue) and the abiltiy to absorb other wavelengths with some manipulation (use of pigments) and still the ability to deflect certain wavelegnths (uva,b) with the use of protectorant pigments.
Danna Riddle is a guy, lol, dont worry I made the same mistake just prior to meeting him. Danas line of thought is that you can measure the absorbance of light and its ability to use it by respiration and by flouresing. The concept on how corals use light is complex but give me some time and I will put a short and skinny together for you. On the color of the bulb yes it is very important to a point. low K bulbs will have no effect or use to a coral. A coral can only utilize light at certain wavelegnths, the rest are useless regardless of intencity.

Give me some time and I will put something together.

Mike
 
T

tankgirl

Active Member
Am catching up, still haven't read the whole thread, but gotta comment on this from Calvo;
it is better to underlight your tank than underfeed your corals.
Click to expand...

I find that hard to believe and doubt if any of us is going to try it.
 
mojoreef

mojoreef

Just a reefer
yea I would have to agree TG, doesnt make alot of sence. Corals are so differing in thier needs, you cant paint this with a wide brush, you have to go individual species.


Mike
 
ScottT1980

ScottT1980

Well-Known Member
So, at least to this point in the discussion, it is fair to say that in fact, kelvin DOES matter, perhaps not directly (although I still have some reading to do here, just way too busy), but it still can affect the PAR value. Is this a correct assumption?

This goes against what I have percieved to be the general consensus in the hobby. I always assumed a 110W bulb or a 400W MH bulb is going to have the same PAR/intensity regardless of kelvin. So true, while kelvin rating does have it aesthetic value, it also does have an intensity value that should be considered. Am I correct here? I am just drawing this conclusion from quick skimming of the actual data (without looking at much discussion, plus that RC thread is going to take me a good two hours to mull over).

TG, I agree and really was shocked to read that.

Take er easy
Scott T.
 
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