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meschaefer

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I would like to discuss an article found in the March 2008 issue of Advanced Aquarist, Coral Coloration and Incident Light: A Photographic Essay. This article was referenced in another post, although I can't remember who posted it.


Some of the information found in this article is making me rethink how I choose bulbs for my MH fixtures. In the past the number one criteria in choosing a bulb has been it's PAR value, while color temperature came in second. I tried to maximize the amount of PAR that I could acheive from the bulb, without choosing a bulb that was to "yellow". As a result I tended to migrate towards 10K bulbs, while avoiding 20K bulbs as their was to much loss of par when compared to those with a lower kelvin rating.

The assumption underlying this choice was that the more PAR, the more photons available for photosynthesis and as a result the best growth. After reading this article, I am not so sure anymore.

quoting from Schlacher, 2007...

After 3 months of grow-out, the overall growth rates under the different bulbs were quite distinct: 6.2 mg/day at 5.5K, 4.9 mg/day at 10K, 8.5 mg/day at 14K, and 10.9 mg/day at 20K. Thus, the bulbs delivering the highest proportion of blue light (20K and 14K) promoted the highest growth rates.

Based upon the above snippet, the 20K bulb had the highest growth rate of all those tested. While presumably the 20K bulb had the lowest PAR rating. (The article did not give information regarding the type of bulb used nor the ballast used for the test, but these assumptions are made based upon Sanjay Joshi's testing)

The article raises a concern about the above test data, pointing out that the bulbs where all placed at the same height above the test subjects. Since the available PAR is somewhat a function of the height of the bulb over the test subject, this would mean that the corals under 10K would have received far greater overall PAR than the corals under 20K, but that the corals under the 20K would have received far greater exposure within the blue spectrum.

If you take a look at the test results as depicted within the photographs in the artice, consistently with the previous test it would appear that in most cases that the corals grown under the 20K bulbs grew faster than the other two test subjects grown under 10K and a T5 array. Not to mention that the corals photographed under 20K bulbs generally had more color.

This leads me to the question, is PAR just PAR or is some PAR better than others? Should I be using higher K bulbs for faster growth. I have always wanted to use higher K bulbs for perceived coloration, but dreaded reduced growth.
 

Bob 1000

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I would love to try a 20k.. But my 12k's are growing my Sps pretty fast about an inch every 3 weeks.. The only thing I have noticed is that everything in my tank is turning 12k blue... My ora red millie now has yellow with yellow polyps... My yellow millie isn't growing nearly as fast as the red..
I will try the 20k next year..
 
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Perhaps a certain MR member who is familiar with the subject can comment on this a bit further :biggrin:

From my understanding ( I haven't read it in awhile) the point of that article wasn't really about growth at all, but rather a corals ability to develop color pigmentation under different lighting spectra and either hold it or change it when moved to a different spectra light.

IME you will never get the growth from a 20K lamp that you will from a quality lower Kelvin lamp. Iwasaki 65K's are still the best pure growth lamp IMO.

Sanjay :screama:
 

meschaefer

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From my understanding ( I haven't read it in awhile) the point of that article wasn't really about growth at all, but rather a corals ability to develop color pigmentation under different lighting spectra and either hold it or change it when moved to a different spectra light.

IME you will never get the growth from a 20K lamp that you will from a quality lower Kelvin lamp. Iwasaki 65K's are still the best pure growth lamp IMO.

This is was my understanding as well, so I was surprised by some of the information I found.

You are right that the point of the article was not really about growth, but there is plenty of information in the article about growth under different kelvin temperature under a controlled setting from two different studies.

The article provides information from another study (Schlacher, 2007), that provides some quantitative data. Furthermore, if you look at the pictures provided showing the growth found in the article, generally speaking the corals grown under the 20K show more growth than found under 10K.
 

meschaefer

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I would love to try a 20k.. But my 12k's are growing my Sps pretty fast about an inch every 3 weeks.. The only thing I have noticed is that everything in my tank is turning 12k blue... My ora red millie now has yellow with yellow polyps... My yellow millie isn't growing nearly as fast as the red..
I will try the 20k next year..


What type of bulb, ballast, and reflectors are you using, and how tall is your tank?

Reds don't show up well as the color temp heads towards blue.
 

Wes

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The article provides information from another study (Schlacher, 2007), that provides some quantitative data. Furthermore, if you look at the pictures provided showing the growth found in the article, generally speaking the corals grown under the 20K show more growth than found under 10K.

Maybe the 20K bulbs were used last in the study? As you know SPS growth increases exponentially the larger a coral gets. If he is measuring growth in mg/day, the larger a coral gets w/ more and more branches, the more branches you have growing, increasing the total mg/day.

EDIT: Nevermind it looks like they ran the study in simultaneously

My superman milli.. Grows out that fast.. And it's a millie..

Millies are the fastest growing acros in my tank...
 
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meschaefer

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Tank is 24" tall.. 400watt Reeflux 12k bulb 7" off the water, Coralvue ballast, luminarc reflectors... Most of my Sps are between 4 and 9" away from the top..


Just so we can keep some information straight, according to Sanjay's sight your lamp and ballast combo has a PPFD of 125.

He doesn't supply a color temp for this combo, but it is noted on the spectral plot that the combo has a very strong peak at about 450 nanometers.

This does not account for your reflectors (which are one of the best), nor does it account for distance between the coral and the lamp.
 

Wes

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Wes,

What is your ballast and bulb combo, as well as the type of reflector you are using.

2 x 250w Aquaconnect 14K SE on icecap ballast, pfo "spider style" reflectors.

I also use 2 VHO SuperActinics.

Millies were the fastest growing Acros for me when I used T5 HO as well.
 

meschaefer

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2 x 250w Aquaconnect 14K SE on icecap ballast, pfo "spider style" reflectors.

I also use 2 VHO SuperActinics.

Millies were the fastest growing Acros for me when I used T5 HO as well.

According to Sanjay's sight the bulb and ballast combo has a PPFD of 83, no color temp listed but as with Bob's combo the spectral plot shows a large spike at about 450.
 

Wes

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According to Sanjay's sight the bulb and ballast combo has a PPFD of 83, no color temp listed but as with Bob's combo the spectral plot shows a large spike at about 450.

As far as color temp goes to the naked eye the aquaconnects seem more "crisp" than the 250w reeflux 12k. But maybe it's just because they are brighter...
 

kris

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Great post Matt. I don't think it's any coincidence that coral farmers like Tyree, Fragfarmer,CAReefer and locals like SMCooler and Pnoyreefer all use 20K bulbs.
 

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