PAR meter- useful tool or toy?

[zygote2k]

If you looked at the PAR meter thread, you might have seen where I told Frankie G that it's useless.

I know him personally, so I felt I could make a response of that nature on the forums.

We spoke on the phone today about the subject and I've come to the conclusion that the PAR meter is nothing more than a toy that's fun to play with.

At one time I was excited to play with it and I took all sorts of measurements with all sorts of tanks and light systems and then I passed it on. Many people did the same. But yet we all failed to do one important thing:

Validate the results.

Sure, we got some numbers here and there, hither and yon but there's simply never been an attempt to define the light requirements of any given coral. I told this to Frank today and I'm convincing myself that it's true.

What say you?

Toy or Tool?

[smallreef]

I say toy...especially for non-traditional lighting systems like LEDs...

Being many incandescent bulbs are listed by par it's hard to validate the difference shown between LEDs and say t5's

While the numbers might be 2-3x higher...what does that really mean for our corals and light needing animals like anemones and clams... We don't really know...

My clams did great under 6 T5's and great under my d120's

So as you say it's light and it will grow things...and I partially believe that...it's just so hard to validate what intensity differential is making a difference...

[Coral Hind]

I also say pretty much a useless toy for LEDs. If you still run MH or fluorescents I see value in it. Now that I only have LED's I just gave my PAR meter away to another club member.  

[Origami]

The right meter is a tool in most cases. Ours is not that meter. The right one costs around $10,000. For some light technologies, ours works great. But, as more and more of us have been moving toward LEDs, especially those of us that have 50/50 mixes of RB/WHT LEDs, our meter approaches being a toy. This was the subject of Dana Riddle's talk at MACNA this year. He said that the paper would be published soon. I've been trying to get information about when because I think it will be of great interest to this community.

 

Sent from my phone

 

 

[zygote2k]

I saw it as a tool for measuring the light intensity if you were concerned about terrestrial plants grown indoors getting enough light or trying to replicate a sunny area accurately.

Even when it was being used with MH systems, no one bothered to start a reference or database that said, " if you have 200 par over this type of acropora, it will result in X".

This is my rationale that it's merely a toy and serves no practical purpose.

[Coral Hind]

I think it served a purpose with MH as you could determine what the output of new bulbs were and then track the bulb as it aged to decide when it was a good time to replace the bulb. It also helped me to make sure corals were placed in the spots where the lighting was better suited for them. Because reflectors for MH do not always spread the light evenly the meter helped to make sure the light in the area you were moving it to was close to where it came from. There were basic charts out there on the web that had ranges that certain corals liked, I guess you just never researched that before making that conclusion. There were also lots of tank pics with other reefer's readings on them so you could compare the PAR readings with your corals and adjust the placement if you wanted to.

[monkiboy]

i got one myself to compare results within my tank. so given the results are around 10% off and you can pull up specific studies for individual wavelengths deltas, they are consistent within my tank. if a nem is doing well under 300 and i have a clone, i can predicate that the next nem will do well in similar lighting. a lot of times, i think an area is similar in PAR/PUR and because of a shadow, how the light is angled, a myriad of factors, i'm completely wrong. also i have three tanks with the same fixture, so i can compare between tanks and make adjustments. it is also just fun to play around with so i see it as both, toy and tool. i certainly wouldn't go to my friend's house that has an AI or radion and try to compare results.

[zygote2k]

 There were basic charts out there on the web that had ranges that certain corals liked, I guess you just never researched that before making that conclusion. There were also lots of tank pics with other reefer's readings on them so you could compare the PAR readings with your corals and adjust the placement if you wanted to.

I agree- there are some charts out there but the numbers vary wildly from chart to chart. Still nothing comprehensive enough to make anything more than a guess. (nice zinger btw) 

[Origami]

a lot of times, i think an area is similar in PAR/PUR and because of a shadow, how the light is angled, a myriad of factors, i'm completely wrong.

Another factor, and it's a big one, is the spectral response of the meter compared to the spectral response of the coral. The Apogee sensor had long been known to underestimate PAR in the blue and, to a lesser extent, the long red ends of the spectrum. As it turns out, there's a lot of photosynthesis that goes on in the regions. That is, light in these bands continues to stimulate photosynthesis in the history coral's zooxanthalle. For the Apogee sensor, it means that it underestimates the light in these areas giving a low reading. It also means that it's really hard to compare performance between lights when the mix of LEDs varies so widely. The LiCor meter that is used by the pros is a much more accurate device.

 

The Apogee meter may have been more useful at one time when the spectra were more balanced, or at least the lamp selection was more limited. But it's less so today because of the huge variation in color configurations that you can get with LEDs.

 

The one thing that you can rely on, the though is, since it underestimates, if you get a reading and the PAR is higher than desired, it is indeed qualitatively high (and most likely higher than the reading it's reporting).

 

 

Sent from my phone

 

 

[basser9]

I have had one for as long as i can remember and as a reefer who had

 every light there ever was from mercury vapor to regular 40 watt daylight tubes

 to every type of mh reflecters and at least a dozen diy led builds i think its

 silly to even suggest there lack of value.

Certain sps need at least 400 par to color up [purple monster] and most monti s

 have issues when exposed to 500 par and above.

You can not look at any light and judge its par ......par meters are our xrays.

When you have a led fixture that has a small number of leds with optics

 you are creating a false measurement any fixture with a cluster will give

 you a normal reading that is the same as mh readings.

I can not imagine not having my par meter it has been the most important tool

 i have.......period.

[zygote2k]

Basser- can you post some referential numbers in regard to all the corals you have grown over the years?

[Gatortailale]

http://www.advancedaquarist.com/2013/9/review

 

 

Product Review: Apogee Instruments' PAR Meter (Model MQ-200) and Software

By Dana Riddle

[ohaverd]

If you looked at the PAR meter thread, you might have seen where I told Frankie G that it's useless.

I know him personally, so I felt I could make a response of that nature on the forums.

We spoke on the phone today about the subject and I've come to the conclusion that the PAR meter is nothing more than a toy that's fun to play with.

At one time I was excited to play with it and I took all sorts of measurements with all sorts of tanks and light systems and then I passed it on. Many people did the same. But yet we all failed to do one important thing:

Validate the results.

Sure, we got some numbers here and there, hither and yon but there's simply never been an attempt to define the light requirements of any given coral. I told this to Frank today and I'm convincing myself that it's true.

What say you?

Toy or Tool?

I have never used a PAR meter, but commend you on the use of these two words.  Well done sir...  well done...

[basser9]

http://www.advancedaquarist.com/2013/2/aafeature

 

Heres a great study done with leds and different par

 if you notice the only way to do this study is with a par meter.

As anybody with a set of eyeballs can see the higher the par

 the greater the growth....go figure.

There have been a ton of studies on reef corals and par all these

 studies have used a par meter of some sort because par is the

 only way to measure light to your corals.

If you look closely at this study the leds where just blue/rb and white

 which worked fine for all those corals in the study now if you

 look a par of 300 was much better then a par of 50 so how

 do you set up your leds to hit 300 and not 50 unless you have a par meter.

The most important tool i have is a par meter.......

[AlanM]

I think some of the problem with PAR meters and LEDs which were mentioned on one of the threads is that LEDs are such narrow band emitters, and that fact coupled with PAR sensors that are not uniformly sensitive over all wavelengths means it becomes difficult to normalize the data and get a real number.

 

And even assuming you did get a good number, you might have a hard time figuring out if that number is good for coral growth or not. The guys in the article basser9 linked tried hard to do it all science like, and they ended up with inconsistent reaults and mixed up samples, and lots of hedging.

 

I would fall more on the toy side, unless a serious attempt was made to do some data reduction by comparing the spectrum observed with the sensitivity curve and doing lots of corrections. Raw data is meaningless, but there is probably some info in there that could be calculated.

[howaboutme]

As anybody with a set of eyeballs can see the higher the par

 the greater the growth....go figure.

 

Can't you just use those same eyeballs to see if your corals are growing with your light and adjust (change light, light bulbs, move coral, etc) accordingly? Toy.

[basser9]

 

Here is one of many led fixtures i have built a wamas person has it now.

Looking at this fixture you have no way to tell what size tank to use it

 on to support sps.

There are no optics .......only a par meter will tell you unless you like

 to kill a bunch of corals to find out.

VIVID aquariums tank with half leds and mh is a great place to compare the 2

 lights.......they use a par meter........why......because only a par meter works.

Edited September 26, 2013 by basser9

[Origami]

I think some of the problem with PAR meters and LEDs which were mentioned on one of the threads is that LEDs are such narrow band emitters, and that fact coupled with PAR sensors that are not uniformly sensitive over all wavelengths means it becomes difficult to normalize the data and get a real number.

 

And even assuming you did get a good number, you might have a hard time figuring out if that number is good for coral growth or not. The guys in the article basser9 linked tried hard to do it all science like, and they ended up with inconsistent reaults and mixed up samples, and lots of hedging.

 

I would fall more on the toy side, unless a serious attempt was made to do some data reduction by comparing the spectrum observed with the sensitivity curve and doing lots of corrections. Raw data is meaningless, but there is probably some info in there that could be calculated.

Toy or tool? It boils down to the quality of the data that is produced. Poor / useless data = toy. Good / useful data = tool.

 

Dana Riddle has done and continues to do good research into this area linking photosynthesis rates to PAR and spectrum for different emitters. If you believe that photosynthesis rates in corals correlate with growth rates (which may be species specific), then this is relevant research and his experience with the tools he's used is relevant to this question.

 

Part of the problem here is that, in part, we're slamming all PAR meters in part with our experience with what amounts to a look at a hobbyist grade PAR meter (e.g. the Apogee meter). That meter is very limited, as you suggest, and trying to get consistent predictions from mixed up samples is difficult at best. BUT, that goes to the quality of the data which is (for the Apogee meter) limited by the inaccuracy of the measurement tool, not the accuracy of the hypothesis. The hypothesis may be perfectly valid but untestable using this particular tool.  See figure 7 in this article for an graphic depicting why the Apogee meter falls short. See Table 1 for the "Best" compromise settings for the Apogee meter across various wavelengths.

 

Riddle's LiCor meter is not a toy, it's an instrument (tool) that produces higher quality data than the Apogee meter, but one that we don't have ready access to because of its expense. IMO, the Apogee meter, when it comes to narrowband emitters (which often operate outside the uniform sensitivity range of the sensor), has an uneven response that may result in poor quality data, making it closer to being a toy these days.