Reef Lighting - Does anyone understand it?

[GUILLO1]

part of the reason the thread died is because the person who started it got "MOVED ON". Its a shame that people with knowledge who contribute to the forums get booted from RC.

 

[jc-reef]

my head about to explode after stumbling upon this...fantastic read though!!! too bad it died.:sad1:

 

[ruprecht]

part of the reason the thread died is because the person who started it got "MOVED ON". Its a shame that people with knowledge who contribute to the forums get booted from RC.

While some of the information is useful, when the OP starts off with the following paragraph in his first post and no one else sees the problem with it the whole thread comes into question as far as I am concerned.

So.. first thing. PAR. PAR meters measure the entire wavelength of 400-700nm. Higher wavelengths in the Orange/Red area, the photons hit the PAR sensor more often than Blue. Think of a wave.. higher wavelengths = shorter distance between wave peaks, meaning more waves hit the sensor. The meter will then take ALL the photons that hit the sensor and give you an average # of them all, which is the # you see on the screen. Here is the problem. If the Red spectrum is hitting the sensor at a rate of 3 photons to every 1 blue photon and then you get the average of that, it doesn't tell you how good your lighting actually is. Corals in nature rely primarily on the 400-500nm spectrum for the majority of its photosynthesis (higher wavelengths do not penetrate water nearly as much and lower wavelengths, this is why the ocean is blue once you get down to a certain depth.) Higher wavelengths play minor roles in photosynthesis but bigger roles in pigmentation/coloration of the coral. Simply running a tank all in the 400-500nm spectrum will give you good growth and healthy corals, but they probably will not look very good to the eye, and your tank will not look as pleasing to you either.

 

[skh]

Reviving this old thread because of all the interesting discussions. The Dana Riddle Advanced Aquarist articles linked here are excellent. One more to add is her article "The Best Lamp Is..." (http://www.advancedaquarist.com/2008/12/aafeature1).

That article shows that the only aspect of the light put out by the various MH bulbs tested that had an observed, strong correlation with growth rates for one particular coral (Acropora solitaryensis), was the amount of red light (650-700 nm) emitted. The more red light, the lower the growth rate was. The 20K and 14K bulbs used put out the lowest amount of red light and had the best growth rates, while the 10K bulb used put out the highest amount of red light and had the worst growth rates (interestingly, even more red light and worse growth than the 6500K bulb tested).

So it seems that for at least some corals (and potentially for a lot of corals) the key thing to look for is the amount of red light (650-700 nm) emitted. The lower, the better. Whether that correlates well to higher K temperature (as might be inferred from the article) is unclear.

 

[Hookup]

Very nice of you to post this additional study. Thanks.

 

[ReefMonkie]

Very nice of you to post this additional study. Thanks.

very interesting discussion, i just wanted to point out something in relation to a earlier comment of yours:

This study was trying to determine which spectrum of lighting gave the best (read brightest) color, which is too bad. If they had weighted the frags at the begining and then at the end, they would have had a good approximation for growth as well as color.

it is true that dana riddle's article does not mention growth but the paper referenced in that article does include growth rates (Schlacher, T., J. Stark, and A. Fischer, 2007. Evaluation of artificial light regimes and substrate types for aquaria propagation of the staghorn coral Acropora solitaryensis).
A pdf file of this paper can be found here:

http://www.marineaquarium.gr/downloads/light.pdf

 

[Hookup]

Thanks for posting that. I read the abstract and will read the whole thing as well.

 

[Wannabeoceangrl]

I'm sooo not ready for this much ino yet. Why does it have to be so confusing! :hmm2:

 

[Bugcrusher]

This is not rocket science, or doesn't have to be....Blue light pentrates deeper into the water column, therefore over the millenia coral(s) have evolved to utilize those "blue" wavelengths. Red light does not penetrate deep into the water column so was not "genetically" selected as a wavelength to support growth in coral. Those animals from the shallow reef will utilize those wavelengths that give the most bang for the buck/photon. Since all light on the natural reef is provided by the sun...it would seem daylight bulbs to the more "blue" bulbs will give you the health and growth you desire. The fine tuning of your individual tank(s) based on depth and strength of light source is up to you. Probably over simplistic but this is my take on it.

 

[Hookup]

I'm sooo not ready for this much ino yet. Why does it have to be so confusing! :hmm2:

The best thing is this forums is loaded with knowledgable folks and you can get as deep in the science as you want or just go with the flow...

Lights = on - that's good!