The truth about lighting

[ScottT1980]

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.

[tankgirl]

Hi Scott,
Here's a couple of good threads on the subject;

http://66.102.7.104/search?q=cache:u...= en&ie=UTF-8

http://reefcentral.com/forums/showth...pagen umber=1

color and growth

[Maxx]

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/showth...agen umber=26
Nick

[Craig Manoukian]

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.

[wooddood]

good info all thanks.

[Brucey]

Yep, TG and Nick .... good info guys
Brucey

[ScottT1980]

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.

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).

Take er easy
Scott T.

[ScottT1980]

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.

[ScottT1980]

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

http://www.netpets.com/fish/fishnews...ddlewalch.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).

[Scooterman]

http://www.advancedaquarist.com/issu...03/feature.htm

You may like this Scott!

[Witfull]

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]

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

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.

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.

[Scooterman]

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.

[ScottT1980]

Never mind about the wavelength issue, the advanced aquarist article sort of touches on it...

[Scooterman]

http://www.advancedaquarist.com/issu...03/feature.htm