What spectrum do sps/corals see when there's more than one source?

[deepseadan]

Question for you light guys, and this is kind of a difficult question to explain. I just recently switched from 250 watt 14k halides, to aqua illumination sol super blue fixtures. The halides were 14k, and obviously more towards the blue spectrum, and again obviously not full spectrum. The light source was a single 14k source. My aquaillumination sol's have three individual light sources, a 6500k led, a 450nm led, and a 470nm led. Running all three LEDs at 100% gives it somewhere between maybe 12k and 14k to the eye, but are the corals still receiving the full spectrum of light from each individual led (6500k etc).
I guess what I'm trying to ask is, is it a positive, negative, or maybe no difference at all to my sps whether I run just the 6500k alone or one of the blues or both royal and blue? Are the blues just increasing par and penetration, or could they actually drown out the full spectrum and par of the 6500k's?

I'm not worried about the look to the eye, just what's best for coral growth and color. I can always manually adjust the kelvin to enjoy the color.

One other note, I guess this could be true for fluorescent bulbs as well, like using 10,000k, 460nm, and purple bulbs.

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[dzhuo]

I guess what I'm trying to ask is, is it a positive, negative, or maybe no difference at all to my sps whether I run just the 6500k alone or one of the blues or both royal and blue?

It will make a difference. Most likely the addition of blue will help the corals.

Are the blues just increasing par and penetration, or could they actually drown out the full spectrum and par of the 6500k's?

No. They won't drown out the rest of the spectrum.

Lighting can be as simple or as complicated as you want. Primarily there are 2 factors to consider: Intensity and spectrum.

When we perceive intensity, we only care about how bright the light source is. For coral, however, PAR (Photosynthetically Active Radiation) is what matter the most. It's a measurement of how efficient the light source promotes photosynthetic. Most corals (and plant) follow this simple pattern:

2 things that stands out from this graph:

1. Corals are able to use the full spectrum of white light to do photosynthetic. This is contrast to what we used to believe that green and yellow are "useless".
2. The 2 spectrums that promote greater photosynthetic is blue and red. This is one of the 2 reasons why blue is so popular.

Generally speaking, the higher the PAR the faster the grow until you hit photoinhibition (which varies from coral to coral).

Aside from PAR, the other important factor to consider is spectrum and color. The colorful pigments we see from corals are proteins but we only see them in a phenomenon named fluorescence. In order for fluorescence to happen, you need to have the correct excitation spectrum which in turn triggers the emission spectrum. Interestingly, excitation and emission spectrum is not usually the same. As long as the corals are healthy, the proteins are always there, but without the correct excitation spectrum, you will never see them. Unfortunately, beyond this simple understanding things get a lot more complicated because we don't even have a universal agreement of what these pigments are and how they should be named. Different corals will produce different types of proteins which requires different excitation spectrum so finding a single spectrum that works for all corals is difficult. Having said that, a lot of proteins will fluorescence (excited) in the 400 to 500 range of blue light (that's another reason why blue is so popular). Dana Riddle has complied a excellent list of excitation and emission spectrum for lots of acro in this article: Feature Article: Coral Coloration: Fluorescence: Part 1. This is part 1 of a 6 series lighting articles by Dana - an outstanding resource for anyone who truly want to learn a little about lighting.

 

[Chris Lakies]

Basically you have a white light source which is the 6500k cree and has the full light spectrum.

You also have a blue single spike at 465-485nm with the cree regular blue.

You then have another blue spike at 450-465nm with the cree royal blue.

 

[chrishayes]

Dzhuo, you forgot to mention PUR to confuse him even more! lol My god man, youre like an encyclopedia. How do you keep all this info for seemingly every aspect of reefing? Do you database all your sources?

Sorry to the OP, although I feel you got the right answer.

 

[Stupes]

The 6500 is not a full spectrum. You basically have 3 different colors that your eyes perceive as white. So technically the led system you have is not a full spectrum source.Where as your MH was a full spectrum lamp with a peak around the 14k mark.
That being said If you run more of the 6500 than the other 2 you will have more algae growth. If you lean it more towards the blue side you will have the same or better coral growth, with less of an algae problem.

 

[dzhuo]

Dzhuo, you forgot to mention PUR to confuse him even more!

You are absolutely right Chris! I did forget about PUR. However, from everything I have read the relationship between PUR and PAR is basically linear and most modern lamps (the ones I have data on are mostly T5) have pretty high PUR so I assume if you pick any modern fixture or bulb you should never have to worry about PUR.

 

[chrishayes]

To the OP, you can get dizzy reading about reef lighting, especially led. I say this and ive been an electrician for 11 years. Not much of what you read will be usefull to you or your corals unless you are custom tailoring a diy fixture for a particular specimen. Any type of commercially available lighting system will be a compromise, photosynthetically speaking. As most will provide a peak in the blue, yellow/green and red making them "full spectrum". The spectrograhs ive seen of leds seem to provide much more of these peaks in the green/yellow which makes sense since ALL the leds used in the hobby are designed for "human" use and eyes and not yet specific to photosynthesis. Your question is a good one!

After Dzhuo's first post, theres nothing else to add. PUR refers to the specific "light" that a particular organism is able to "use", to be untechnical but get the point across.