# PAR versus Spectrum



## mattcham (Mar 7, 2014)

BML 10,000k XB led has much higher PAR (115 PAR @24" depth) than BML 6,300k XB led (80 PAR @24" depth), but the 6,300k has more red which is a superior spectrum for growing plants.

Which of the two will grow a dwarf baby tears (HC) carpet faster assuming high tech CO2, EI dosing, daily glut dosing, and 24" distance between light and substrate?


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## brad.harper.9 (May 8, 2014)

I'm pretty sure it will depend more on your co2 levels and ferts. The 10000k has more blues that penetrate the water better. The reds are more potent but fizzle out more quickly with any depth.


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## brad.harper.9 (May 8, 2014)

Are you going to have any red plants or are you shooting more for an iwagami type scape?


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## klibs (May 1, 2014)

I think either will be fine. Are you going to dim the fixture? 115 PAR @ 24" is a lot!

I am currently waiting on an order of 1x Dutch XB / 1x 10000K (normal series). It seems I got the last of the normal batch lol - doesn't look like they sell anything lower than XB now.

Picked that combo because PAR is very similar between the two and the light should look nice and balanced.

Like the above user I think it depends on what else you want. If you want reds to pop go with the dutch. If you want only greens then the 10000K will get it done. Both should be great choices.


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## mattcham (Mar 7, 2014)

So there is no clear cut advantage in terms of growth despite 43% more PAR for 10,000k??? The main differences boil down to aesthetics and appearance? (6300k for redder reds, 10000k for greener greens)

Is there a PAR threshold that will produce no additional growth advantage given same spectrum and proper CO2/ferts? For example:
6300k @200 PAR versus
6300k @100 PAR


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## Solcielo lawrencia (Dec 30, 2013)

The 10K provides more plant-usable light so it could grow plants faster.

In an aquarium, the limiting factor that limits plant growth will probably CO2; you won't be able to add enough no matter how powerful the light.


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## mattcham (Mar 7, 2014)

Here are the spectra for 10,000k vs 6,300k from BML, along with Hoppy's image linked from his landmark guide in 2012 (http://www.plantedtank.net/forums/showthread.php?t=184368):










6,300k shown below:









10,000k shown below:









Everyone says that plants are less sensitive to green and yellow wavelengths, but from Hoppy's diagram it seems that the greens and yellows form a very large minority of the response curve.


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## Xiaozhuang (Feb 15, 2012)

Frankly, if you're planning for the long run, HC growth shouldn't be a factor of consideration because it grows quite fast. Once you have a successful carpet, you'd wish growth rates were slower. Its something like - say 150 PAR; HC carpet fully grows in 1 month, but you need to prune every 3 days or say 60 PAR; HC carpet fully grows in 2 months but you need to prune once every 1.5 weeks. The second is much more preferable in the long run, if the quality of HC grown was the same no ? If you have high light/fast growth, but don't have time for maintenance, the tank crashes easily (either algae, or stuff such as HC carpet floating cos it get too thick).

The choice between a dutch and the 10k should be about which one renders color better. The visual effect outweighs any other consideration, and many people have grown plants with a spectrum that suited their plants but their eyes didn't like, and ended up spending more money getting the light that was visually appealing. At the end of the day, aquascaping is still a visual art. (unless you're just doing horticultural sale) 

I own both fixtures (10k and dutch) and frankly I find that the 10k is a bit too cool unless your tank has only 2 colors (green + 1 shade of red). It is okay for moss tanks, or all green tanks or if specific fishes look good under 10k. Visually speaking, unless you like a very cool temperature look to a tank, the dutch renders colors better. I.e. if you like the look of tanks under warm CFLs or other fluorescent lighting, the dutch comes closer to it, and renders oranges, and a variety of reds better. I wanted to post a comparison example in the BML thread but haven't had the time, so that others can make this comparison before buying.

On a side note, I don't want to sound accusatory here (have been down the road myself), but often people try to overcompensate on light after they didn't manage to grow one plant or another. But it doesn't work that way; more light doesn't make up for a lack of a certain nutrient or CO2 or maintenance, what is does do is exaggerate algae issues unless the tank balance is good. Beyond a certain PAR value (about 80-100 at substrate), most plants (few exceptions) don't get better color or growth form, what you do get is faster growth rates ( and more maintenance work ). Perhaps some stuff you can grow a wee bit more densely with the extra light, but on balance, more light = a lot more work.


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## Solcielo lawrencia (Dec 30, 2013)

There are many pigments that react to light, however, not all of them appear to have function. The two main pigments are Chl A and Chl B, both of which responds best to blue and red light. Carotenoids, anthocyanins, et al use spectra between these ranges but don't provide much useful growth. That photosynthetic response curve considers all of these pigments but they are most probably for terrestrial plants. How applicate are they to aquatic vegetation? I don't know.

Also, the radiometric output clearly shows that the 10K is putting out more photosynthetically useable light than the Dutch, which has minimal blue and red in comparison.


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## gus6464 (Dec 19, 2011)

Look at it this way. The 10K is a high PAR light and the Dutch is closer to high PUR with some aesthetics thrown in. High PAR will make the plants grow the quickest, but high PUR will make them look their best.

High PUR is easier to manage in the long run. Not only will the plants look better but also you won't have to trim very often so it doesn't get out of control.

Now of course you can go high PUR and PAR by getting more than one Dutch fixture but once again that will be a huge pain in the ass to maintain in the long run.

The beauty of a high PUR setup is that you can grow the elusive red plants which people love without that much PAR. Sure they will grow slower but in the long run you will be thankful for having less maintenance.

If you want a good example of a high PUR tank look at Tom Barr's 120G. Out of 8 bulbs he has like 2 that are high PAR. His lights are pretty close to the water too and you don't see him complaining about algae.


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## jeffkrol (Jun 5, 2013)

Well.. it also depends on the PAR meter used.. If an Apogee, it can be way low w/ red, and high w/ blue..










i have found no mention of the instrument they use to measure PPF.
You can't "estimate" what you didn't measure.. 

http://www.apogeeinstruments.com/light-intensity-measurements-for-light-emitting-diodes-leds/


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## gus6464 (Dec 19, 2011)

Apogee is the other way around. It measures hot with red and low with blue.


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## jeffkrol (Jun 5, 2013)

gus6464 said:


> Apogee is the other way around. It measures hot with red and low with blue.


The above chart is direct from Apogee..

OK better chart. but still cuts off below 660nm..



















Depending on the 660nm red spectrum spread.. Apogee can "miss" a whole bunch of red..w
it's "precipitous" drop at 650.........
Devil is in the details......... 

Ballpark figure is you could lose 50% of the PAR of a 660nm red LED.......


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## gus6464 (Dec 19, 2011)

jeffkrol said:


> The above chart is direct from Apogee..


And as you can see from the chart it measures hot in the red area and low in the blue area.

So if you are getting 110 PAR on a red light on the Apogee the real PAR is ~100. On a blue light if you are getting 100 PAR the real output is more like 120-130. On a true actinic light the Apogee is off by almost 3-5 times.

Anything above 660 is barely used in the aquarium world so it doesn't matter. Blue and violet on the other hand is used extensively in reefs so it matters a lot. It also matters for planted tanks because 6500K LEDs are blue dominant which means that you will be putting out a lot more PAR than what the Apogee says.


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## jeffkrol (Jun 5, 2013)

gus6464 said:


> And as you can see from the chart it measures hot in the red area and low in the blue area.
> 
> So if you are getting 110 PAR on a red light on the Apogee the real PAR is ~100. On a blue light if you are getting 100 PAR the real output is more like 120-130. On a true actinic light the Apogee is off by almost 3-5 times.
> 
> Anything above 660 is barely used in the aquarium world so it doesn't matter. Blue and violet on the other hand is used extensively in reefs so it matters a lot.


your not defining red correctly.. 
ONE type of red:
Red (635 nm peak, 10 nm FWHM)
4.7%

660 PEAKS at 660 where the apogee range is already sharply sliding.. On a 15 LED bar w/ 2-660nm red w/ unreported PAR of say 50% .. is somewhat a "big deal"........


IF I had a light bar of 100% 660nm LED's how "off" would the Apogee be?? Please don't say it would oversample.. 

Gee go figure:


> The broadband white LEDs output a small proportion of radiation beyond the upper end of the Apogee quantum sensor/meter sensitivity range (665 nm), and thus yield low measurements for the white LEDs.


http://www.apogeeinstruments.com/light-intensity-measurements-for-light-emitting-diodes-leds/


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## gus6464 (Dec 19, 2011)

jeffkrol said:


> your not defining red correctly..
> ONE type of red:
> Red (635 nm peak, 10 nm FWHM)
> 4.7
> ...


It would be off close to 20% hot. So the 100 PAR on the Apogee would actually be 80. Not a big deal because of red penetration distance but when you have cool white:

A PAR reading of 70 on a cool white LED is actually close to 100.

When I say red I mean red that is most commonly used in aquariums which is 630-660.

In reefs this can kill a tank. On lights that are violet 400-430nm heavy a PAR reading of 100 on the Apogee is more like 300 in real life. That will cook corals real nice.

If BML isn't using a LiCor on their reef lights to measure then they shouldn't be selling them.


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## jeffkrol (Jun 5, 2013)

gus6464 said:


> Anything above 660 is barely used in the aquarium world so it doesn't matter.


see Apogee comment of undersampling "white" LED's...



> *The broadband white LEDs output a small proportion of radiation beyond the upper end of the Apogee quantum sensor/meter sensitivity range (665 nm), and thus yield low measurements for the white LEDs. *


gus your arguing to argue...


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## gus6464 (Dec 19, 2011)

jeffkrol said:


> see Apogee comment of undersampling "white" LED's...
> 
> 
> 
> gus your arguing to argue...


Um there are countless of different "white" LEDs. And who is arguing? You stated that Apogee measures low on reds and high on blue when it's the opposite.

So now you are saying a 12K white is the same as a 3500K white? The greater the blue spectrum on the white LED the more the Apogee will be off.

That Apogee documentation is quite outdated and came out when LEDs were still fairly new. It doesn't take into account high CRI LEDs which have more red than blue.

Bump: Math was wrong on my post above.

660nm LED
Apogee PAR 100
Real PAR 80

445-450nm LED
Apogee PAR 70
Real PAR 100

You keep arguing about red LEDs but show me an aquarium light that has a red LED greater than 660nm.


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## jeffkrol (Jun 5, 2013)

> IF I had a light bar of 100% 660nm LED's how "off" would the Apogee be??





gus6464 said:


> It would be off close to 20% hot.


that is contrary to every fact from Apogee I presented..










1/3 of a 660nm LED output is past the stated cutoff (665) of the Apogee......IF you take into account the sharp slope of the cutoff......
Yes blue is under sampled.. I moved to a more pressing issue.... 



> *output a small proportion of radiation beyond the upper end of the Apogee quantum sensor/meter sensitivity range (665 nm)*


I'm not sure I can make it any plainer........but I will let Apogee try......


> IMPORTANT NOTE: LEDs that output a large proportion of radiation above approximately 660 nm will read very low and should not be measured with an Apogee quantum sensor/meter.





> As expected based on
> litereature provided by the manufacturers, the Apogee sensor underestimated the
> response of the blue LED @ 444nm and the red LED @ 660nm. This is because the sensor
> does not respond well to wavelengths below ~450 and above ~650. If reporting radiation in
> ...


http://www.ces.uoguelph.ca/TechNotes/TechNote_004-2011.pdf











to save reading..


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## jeffkrol (Jun 5, 2013)

gus6464 said:


> If BML isn't using a LiCor on their reef lights to measure then they shouldn't be selling them.


From digging around BML.. I pretty sure they use an Apogee.. No "direct"
proof though. Haven't found any mention of what they use one way or another..

considering Apogee and "Apogee like" things are probably more common in the "real world" outside of research I can understand that.... on a commercial basis.

Now they may "manually compensate" because it is obvious they understand the error..
http://forum.buildmyled.com/index.php?threads/apogee-mq-200-to-measure-par.432/



> Since a third of the LEDs in the Super Actinic fixture are 400nm UV LEDs, the Apogee is going to miss much of this PAR. It will also under-report the power from the 450nm Royal Blue LEDs in this fixture. The fall-off in the deep red region will also miss some of the PAR from the 660nm deep red LEDs in the 14000K fixture (which also uses some 400nm UV LEDs).
> 
> Hence, you will need to use this chart to make approximate adjustments to the PAR values that are reported on the Apogee.
> 
> ...


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## klibs (May 1, 2014)

Xiaozhuang said:


> Frankly, if you're planning for the long run, HC growth shouldn't be a factor of consideration because it grows quite fast. Once you have a successful carpet, you'd wish growth rates were slower. Its something like - say 150 PAR; HC carpet fully grows in 1 month, but you need to prune every 3 days or say 60 PAR; HC carpet fully grows in 2 months but you need to prune once every 1.5 weeks. The second is much more preferable in the long run, if the quality of HC grown was the same no ? If you have high light/fast growth, but don't have time for maintenance, the tank crashes easily (either algae, or stuff such as HC carpet floating cos it get too thick).
> 
> The choice between a dutch and the 10k should be about which one renders color better. The visual effect outweighs any other consideration, and many people have grown plants with a spectrum that suited their plants but their eyes didn't like, and ended up spending more money getting the light that was visually appealing. At the end of the day, aquascaping is still a visual art. (unless you're just doing horticultural sale)
> 
> ...


+1 for this entire post

It's not all about light. Either fixture will be enough to get the job done. I bought both not for the intensity but rather for the spread and how the combo renders colors.


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## mattcham (Mar 7, 2014)

Thanks everyone for the interesting discussion. I understand that "with great lighting power comes a great deal of maintenance," which is why it is nice to have the BML dimming feature. Crank it up during propagation, dim it down when propagation complete.

I actually already have the 10000k XB BML, but am really tempted to also get the new 6300 MC beta model, which so far only comes in 6300 dutch temperature (and 80 PAR at 24" depth). My needs are somewhat unusual due to 24" depth and I wasn't sure if there was a clearcut winner due to PAR vs spectrum differences, and 80 PAR is barely at high light level. This thread was very helpful in clarifying to me that the 10000k has better growth potential at 24" depth and that the main (only?) advantage of 6300k at 24" depth is aesthetics which is of critical importance for red plants.


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