[monkeyfish]

Great thread, definitely sticky worthy. Subscribing as the next two tanks I have planned will be getting LED's for sure.

 

[samamorgan]

Added some educational information on spectrum pertaining to LEDs.

 

[madness]

Great thread. Not sure how I didn't notice it before.

 

[Hoppy]

Not all spectrums are created equal!
Analyzing photosynthetically active radiation (PUR)

One of the reasons LEDs can be so much more efficient than T5, compact flourescent, and even metal halide is spectrum output. The chlorophyll pigment is green in color, which means that it reflects the green spectrum of light to our eyes so we see it as green. This means that it absorbs all other spectrums of visible light. Check out this graph:

As you can see, plants absorb visible light very well between ~400-500nm and ~650-700nm. The absorbtion rate drops off significantly in the green and yellow spectrums.

LEDs put out very specific spectrums of light, which are defined by the manufacturer. LED manufacturers can fine tune emmiters to put out exactly the spectrum specified by the client. Since PAR meters measure light between 400-700nm, an LED array putting out less par than a broad spectrum flourescent fixture may actually be putting out more photosynthetically usable radiation (PUR).

Why is this concept important?
Say two LED emmiters read around 100 PAR on a meter. The first LED spikes highest in the 550nm range. The second LED spikes highest in the 450nm range. So while both emmiters have the same PAR value, emmiter two would actually grow plants very well because it is in a range that can be absorbed by the plant, while emmiter one would probably keep plants limping along, if they could even survive.

Just because plants are green doesn't mean they reflect all of the green parts of the light spectrum. It means they reflect more green than red, primarily, and blue secondarily. Another reason plants look green is that our eyes are very sensitive to green, but not at all sensitive to red. But, plants absorb all parts of the spectrum to some extent. Most LEDs don't have the very high spikes in output that we see with fluorescent lights. The ones I have seen have a peak, for sure, but it is a broad one, and there is still a lot of light emitted that isn't in that peak.

Until we know how much PAR we are getting with various lights in various configurations it makes little sense to try to complicate matters by also worrying about PUR. PUR was of much more importance when it was hard to get enough light to grow plants, and anything that would increase the amount of usable light we were getting from a light fixture was something good to pursue. Now, the biggest lighting problem we have is having way more light (PAR) than we can easily use on our tanks. So PUR becomes much less relevant.

I find the collecting of PAR data for various manufactured LED light fixtures very useful, and I hope we can expand it eventually to include all such lights that are available. Let's not complicate it.

 

[samamorgan]

I actually added this because i see a lot of questions like "why wont my incandescent/actinic lights grow plants? I've got enough wattage!"

I know that light reflection and human eye perception is much more complicated that i made it out to be, but actually adding that information in there would just complicate the idea i was trying to get across. You can see in the chart that the other spectrums are absorbed by the plant to a point, but not at nearly the rate that the proper spectrums are.

Also, wouldnt this factor in quite a bit from emmiter to emmiter? I know a lot of fixture manufacturers order patented emmiters from cree that put out the spectrums they want. Those patented emmiters vs a regular cool white would be significantly different in useable plant light, right?

If you really think this complicates things too much or its really just not useful end-user information, i'd be glad to take it down. If you think it is useful and can think of a way to improve the information in a concise way, i'm all for editing it. I'd like this thing to be a knowledge base from the community - for the community, not just from my point of view.

 

[manini]

Great information on LED lighting. I am about to begin my experiments on the AI Sol product on a 18 gal tank. Cant wait to see what kind of results I will be getting.

 

[samamorgan]

Great information on LED lighting. I am about to begin my experiments on the AI Sol product on a 18 gal tank. Cant wait to see what kind of results I will be getting.

Nice! I kinda wanted to get that fixture myself, but it's so much moneys!

 

[WingoAgency]

Great information on LED lighting. I am about to begin my experiments on the AI Sol product on a 18 gal tank. Cant wait to see what kind of results I will be getting.

That seems VERY OVERKILL! 24 3-5W over a 18G! Do you mean the nano?

 

[samamorgan]

That seems VERY OVERKILL! 24 3-5W over a 18G! Do you mean the nano?

I thought this too, have to hang it pretty high

 

[akpoly]

I have some TrueLumens that I just got. I'm waiting for my hands on a par meter. I can let you know what those get once I find out.

 

[monkeyfish]

I sent a request for info on the trulumen pro fixtures to current-usa. I'll post their response if i get one.

 

[JoeGREEEN]

SUBSCRIBED

I smell a SticKy on this
Awesome!

 

[ucantimagine]

So to bottom line this, if we can: Is LED made specifically for aquariam lighting better than, equal to or not as good as a comparable T5 HO light?

 

[galabar]

Not all spectrums are created equal!
Analyzing photosynthetically active radiation (PUR)

One of the reasons LEDs can be so much more efficient than T5, compact flourescent, and even metal halide is spectrum output. The chlorophyll pigment is green in color, which means that it reflects the green spectrum of light to our eyes so we see it as green. This means that it absorbs all other spectrums of visible light. Check out this graph:
View attachment 40237
As you can see, plants absorb visible light very well between ~400-500nm and ~650-700nm. The absorbtion rate drops off significantly in the green and yellow spectrums.

LEDs put out very specific spectrums of light, which are defined by the manufacturer. LED manufacturers can fine tune emmiters to put out exactly the spectrum specified by the client. Since PAR meters measure light between 400-700nm, an LED array putting out less par than a broad spectrum flourescent fixture may actually be putting out more photosynthetically usable radiation (PUR).

Why is this concept important?
Say two LED emmiters read around 100 PAR on a meter. The first LED spikes highest in the 550nm range. The second LED spikes highest in the 450nm range. So while both emmiters have the same PAR value, emmiter two would actually grow plants very well because it is in a range that can be absorbed by the plant, while emmiter one would probably keep plants limping along, if they could even survive.

Would it be possible to roughly estimate this by using green and yellow filters? If you were to get some photographic filters that block the green and yellow light that aren't all that useful, you might get a better idea of the PUR values of these LEDs.

 

[samamorgan]

I sent a request for info on the trulumen pro fixtures to current-usa. I'll post their response if i get one.

Sweet! I've got an email sent their way about a week ago with no response yet. The more people that chime in the better.

List of who I contanced on the mass email sent out 1/08/2012:

• AquaticLife -responded, information added
• Current USA
• EcoTech - responded, useless information
• Ecoxotic
• Elos
• Hydra Aquatics
• Ista
• JBJ
• Kessil - responded, information added.
• Marineland
• Maxspect - responded, information added
• Orphek
• Tropical Marine Center - responded, information added
• UP Aqua

The fact that its been over a week now and i havent gotten so much as a wink from most of these manufacturers is kinda disheartening. I would think that the prospect of free advertising and the potential for a broader customer base would be extremely appealing. For those who did respond so far, most responded within the first two days. Good customer service for the win!

 

[samamorgan]

Would it be possible to roughly estimate this by using green and yellow filters? If you were to get some photographic filters that block the green and yellow light that aren't all that useful, you might get a better idea of the PUR values of these LEDs.

That's an interesting idea. I honestly don't know if that would work or not, but it sounds reasonable. My thought is: if it was really that simple, wouldnt the manufacturers already have done this to their sensors?

 

[samamorgan]

Here is the response i got from Kessil:

Hello Sam,

Thank you for presenting us with this opportunity.

We currently do not have official PAR measurements. There are people who have done so and I can include a link. What we have found is that the value even between units that perform the same differs greatly. We also see that different meters have different results and some do not measure UV or near UV. This is one of the reasons we spend over 1 year of independent testing on reef tanks, and we allowed our local stores in the SF bay area to test first hand as well.

I hope this link helps and feel free to let me know if you have any questions. I get a lot of feedback that Post #10 & #114 are very helpful to end users. http://www.reefcentral.com/forums/showthread.php?t=2040877&page=5

Best Regards,

David Lowry
Sales Manager

Oddly enough, i found post #71 to be more relevant.

 

[WingoAgency]

Par data of couple Edge Saviors

 

[samamorgan]

Par data of couple Edge Saviors

Im now noticing that you don't have a website for information on your products. Could you put up some kind of site I can link to for consumer direction? The par values don't help anyone if they can't access the product.

 

[madness]

So to bottom line this, if we can: Is LED made specifically for aquariam lighting better than, equal to or not as good as a comparable T5 HO light?

From what I have read the answer is probably 'better.'

One benefit of LEDs is that they can mix different spectrum LEDs in one fixture to target specific spectrums of light whereas in flourescent lighting they have to coat the bulb with a specific phosphor to get a certain wavelength light out of the bulb and I think that there is a limit to how many different phosphors that they can efficiently use.

That doesn't even address secondary features like energy savings, dimming features, light penetration, increased life span, ability to create 'shimmer', etc.