# PAR - the real way to measure light



## neven

What does that mean to us? well watts per gallon is dated and only meant for average sized aquariums with t8 bulbs, and the hobby has veered far away from that. More and more you see par data out there now, since its the only factor that remains constant through all the lighting methods. It is a measure of photon radiation in the wavelengths plants use for photosynthesis. here is the chart of what each level of lighting is.

*Low Light:* 40-70 μmols/m2/s
*medium:* 70-150 μmols/m2/s
*High:* 150-300 μmols/m2/s
*Very High:* 300-600 μmols/m2/s

To get these readings though, you require a PAR/Quantum Meter. They are pricey, $350 to be exact. Many aquarium clubs will purchase a meter just so their members have access to these readings without bearing the full brunt of the cost. Im unsure whether Vancouver's club has their own par meter. At the end of this, i'll mention a cheaper way for those wishing to get their own.

Now how to use the meter, the primary use is to figure out just how intense lighting we need. if you purchased your hood already, it can be varied through using different number of bulbs and changing the height (and orientation) of the fixture. CFLs can be varied quite a bit compared to your standard hood. No longer are we forced to simply lesson our photo period to reduce algae.

Now to figure out where to take your readings. Place the par meter probe on the substrate in several readings and chart your tanks foot print with the number read outs. Adjust the height then check those areas again. if you are not injecting CO2, stay in the low light threshold, you can still grow plants like HC if you know how to balance your nutrients. For typical Co2/excel EI dosed tanks, Medium threshold is recommended, try to stay under 100 μmols/m2/s if you want to keep the trimming low.

For those with no access to a meter, theres several sources in which you can compare to, With PAR readings charted with different fixture heights and orientations, you can greatly reduce the guessing game and hit your wanted light level much easier.

---Added later---
Still haven't heard of who rents meters here, but there are a couple sources i'll link that are helpful in figuring out lighting distance without a meter, based of par readings and tests from other hobbyists. I recommend any hobbyist give them a read

For *Linear Tubes (ie t8, t5, t12, etc)* PAR vs Distance, T5, T12, PC
For *CFLs* PAR Data-Spiral Power Saver Bulbs, lighting question - Page 2

Why tanks with raised lights do better: Light Height above Tank

To the mods, apologies for links to other forums, but this information is too good to pass up. For a while now i've used the charts for lighting recommendations to others, figured i might aswell link the source.

If your lights dont cover the whole tank length, the only real issue is when the light is close to the tank top, then you see the spread of the light in the water. I generally plant less demanding plants in dim lit areas anyways
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Now as for a cheaper way to make your own meter. You simply buy the probe, the Apogee SQ-120 Probe is the cheapest and calibrated for fluorescent lighting.

Some more facts on the sensor:
Calibrated to exactly 5.00 μmols/m2/s per mV
the cable is 3meters long (9feet), ends are your standard pigtail
There are correction factors you need to apply the closer your source is to sunlight, ie, fluorescent = 0%, MH = 2% lower

for us though, the levels of light we need, you can ignore the correction factor completely as it'll only be a few μmols/m2/s off at the substrate level.

What you do is buy metal gator clips ($2 for two most likely), use a digital multimeter at the millivolts setting ($10 for a cheap one), and multiply the result by 5. Now you got your PAR Reading in μmols/m2/s. Just don't put your multimeter on the Ohms setting with the probe attached, you can damage it. Also don't touch the probe pigtails together, as the probe is its own power source.

Personally i do not own one or do not have access, the CFL thread on another forum allowed me to guess work quite accurately where i lay light wise. I have read much into this on other forums, through googling the subject and through apogee's website, and i do plan on one day getting my own probe to test with  I do hope that this forum if they have people with these meters, can gather its own information to share, so members shake the dated watt's per gallon idealogy.


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## Nicklfire

Good Read :0, I think BCA is just starting to get into the PAR reading information. We don't have very many at all floating around the forum but i think it would be a great thing for us to get a few going.

There is a PAR meter that you can rent around on this forum, i forget who has it right now.


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## Mferko

what the heck is a PAR?
ive done commercial lighting calculations before and its always lumens/area taking into account how reflective the surfaces are and how high the lights are from the surfaces etc etc.
theres some pretty handy computer programs out there to do all the calculations for you
youd also take into account the type of color rendering needed etc etc but for aquarists there aren't nearly as many options.


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## davefrombc

PAR ( Photosynthetically active radiation) is the measure or the useful light reaching plants. You can have blindingly powerful light, but if it is of the wrong wavelengths , it is useless to your plants.
Lumens/area, ( LUX ) is a measure of the light intensity that is visible to the human eye. A high LUX rating does not mean plants will do well if the spectrum is not good for photosynthesis..... but you will be able to see the plants failing easily.
Light that is bright and pleasing to our eye does not necessarily mean it is what plants need . We can guess how good a light will be for our plants , and for our viewing pleasure by checking its colour spectrum, CRI ( Colour rendering index) and lumen output, but for the plant obscessed, must have everything perfect for that show winning tank person, a PAR meter is high on their "must have" list; just as light meters are a necessity for the dedicated photographer, and stage lighting people.


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## neven

i had a much more long winded response but dave beat me to the punch 

But as for CRI, most of the bulbs we use for fresh water plant growing tends to be focused around 5000-6700K bulbs, and in those ranged you'll find the CRI to be decent for most manufacturers, whether its cfls or t5s. Im also taking general use bulbs into account, as many of us don't buy bulbs made for the aquarium, just bulbs we've found our plants to grow well under. This data is atleast written on the packaging in most cases  Just make sure you read nickelfire's sticky, as it goes into temperatures and such.

With par readings, you can greatly limit the excess light your aquarium might be receiving, and use light as the limiting factor with some accuracy. After all, if you just exceed the required PAR for your plants in the tank, you'll be promoting a bit more growth (as long as nutrients and carbon are there), and greatly limiting the unneeded light that algae can thrive off of.

BTW If those with meters to rent wish their names to be mentioned i can make note of it in the original post.


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## fkshiu

A few of us reefies chipped in for a Quantum meter. Here's an example of some old readings with my tank:


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## neven

awesome example of par readings  i never thought that marine would find par meters useful, figured the light spectrum they require to thrive would be a broader range than the par meter


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## 2wheelsx2

Photosynthesis is photosynthesis, whether it's corals or plants. Unless it's bacterial utilization, I would think a PAR reading is meaningful.


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## neven

yea i read into it after seeing the tank readings  i just never have looked much into corals


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## SeaHorse_Fanatic

A couple of years ago, a bunch of us local reefers chipped in together to buy a PAR meter to test the PAR output from our high powered reef tank lighting.

It works great and takes the guess work out of it.


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## neven

-edit- moved to first post


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## 2wheelsx2

You can always buy one and rent it us to the planted tank nuts here.


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## Nicklfire

2wheelsx2 said:


> You can always buy one and rent it us to the planted tank nuts here.


I might have to do that  Just Rent it out until it's paid off, then free to use after that , might ahve to save up a bit more lol


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## 2wheelsx2

Do you know where to get one Shawn? I've been thinking about one. Maybe mini-GB?


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## neven

there are two methods, you can get the probe, connect it to a volt meter, at the millivolts setting, and just do the math in your head (multiply by 5) to get you PAR.

Saves about $200 i think that way, but that only works when you are getting it for yourself, if you are renting out people will want the full package


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## 2wheelsx2

I found the Apogee on here. Aquarium Specialty

You can rent one here, but the deposit is steep: Rent PAR Meters at Global Aquarium Supply

Or you can rent Anthony's.


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## beefORchicken

thanks for the post. i'd love to check this on my tank and all it's fixtures. maybe i'll try creating a par meter, sounds easy.


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## Nicklfire

2wheelsx2 said:


> I found the Apogee on here. Aquarium Specialty
> 
> You can rent one here, but the deposit is steep: Rent PAR Meters at Global Aquarium Supply
> 
> Or you can rent Anthony's.


Tom Barr has done a couple of group buys a while back, i was going to go into it the last time but just forgot. I'll ask him what type they were, and see if i can get a price, i'm sure he's got a couple spares or know of someone. Worst case i just gotta pay full price at the place he ordered from.


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## someguy

how bout the LED's how are they measuring up on the PAR


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## neven

Well LEDs are quite the broad spectrum, it would come down to specific lamps/fixtures needing to be tested


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## EDGE

Here is a pdf from Philips lighting briefly explaining PPF, micromol,

http://www.search.philips.com/searc...ltural/pdf/philips_growing_your_profit_nl.pdf

These bulbs are for greenhouse use and not so much for aquariums. They do have ceramic metal halide which works great for fresh water planted aquarium.

Philips also have LED grow lights, but I haven't gotten a reply if they are only in the UK or if they are globally available.

Just found this. Here is a more renowned greenhouse light company slide show done back in 2008 (without the commentary). They do have diagrams on LED and a comparison between the different color LEDs wavelength and micromol. Will have to do a bit more information gathering as the speaker claimed that micromol alone is not a good analysis for light efficiency. Something to do with Efficiency lichtsource (lm/W)

http://www.canadiangreenhouseconference.com/talks/2008/2008-TK-Napper-PLLight.pdf


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## neven

I have 2 new tanks i needed to figure out what sort of lighting to go for. Because im stuck with a fixed distance to mount the lights, i wanted to choose the best light source for the distance above the substrate. As always when im faced with light questions i resort to the Par Vs Distance charts on planted tank

PAR vs Distance, T5, T12, PC - New Chart

This time however i noticed they had a new chart for t5ho reflector qualities with pictures to demonstrate what is each quality. This is a very important piece of information i figured people should know, as it demonstrates the vast difference of output a reflector can boost the fixture. Plus it helps us dial in our target PAR range even more.

For me i have 18ish inches above the substrate, so correlating from the t5ho graph, a single strip of t5ho fair reflector quality should do it for me. J & L has cheap t5ho's with built in reflectors that look similar to their example of a fair fixture, so now i can make my purchase without having to worry about my light causing algae issues.

Prior to the t5ho reflector graph, the result would have been that i'd be using a PC fixture or 2xt8 fixture. The Fixture would be bulkier most likely, and i'd be forced to buy more variety of bulbs whereas i have t5hos already 

The same author of the thread also wrote the article (different format) here: http://www.aquabotanic.com/?p=1484

and another good read:
http://www.plantedtank.net/forums/lighting/118454-light-height-above-tank.html


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## gklaw

Hey Rob:

Surprise you done have a millivoltmeter in your family 

I have a decent multimeter. You you can get the parts, I will pay for them and we can make one. I probably have a couple of alligator clips kicking around as well. Want a weekend get together project.

I am not a hi-tech guy when it comes to planted tanks. But for the fun of it - why not. Not sure about renting it out to just anyone on the forum though - sure for some. Blow the meter and I am $200 out of luck and no toy to play with when I want to be a ******* electrician. Cannot blame anyone on high deposit on sensitive electronic equipments.


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## neven

Of course i have a multimeter, i'd make a pretty crappy electrician if i didn't, lol.

As for the par probe, it would be handy having in the community especially when it comes to testing the new LED fixtures, but for planted tanks with other fixtures, the graphs really do a great job and they eliminate a lot of issues the watts per gallon had. I've used their Twister CFL chart before (PAR Data-Spiral Power Saver Bulbs, lighting question - Page 2) as well as their t5ho and i've found after that i had to make very little adjustments to eliminate BBA growth compared to when i just guessed what i needed and scratched my head in wonder at the black fur overtaking every plant and piece of wood in the tank


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## gklaw

Sorry. Missed the $150 probe part 

Not sure if I want another expensive toy


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## verkion

Hrm...I'd love to test the PAR of the 20W Prime LED Emitters I have sitting here at a variety of depths. So is there one floating around on the BCA forum somewhere? I'm trying to figure out whether I should get a mixture of Cool, Neutral and Warm White LEDs or just be lazy and run the Cool White (6700K) ones.

Thanks!
verkion


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## rstampa

How can I determine my par? I have 2 LED fixtures on my 65 gal planted tank. One is dim-able and the other is not. The are both 36 ins long with several colors and are around 20 watts each. 
Every forum I read, they use T8, T12 etc. But I can't find anything on Par LED lighting
Could anyone please help me.
Thanks


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## Reckon

rstampa said:


> How can I determine my par? I have 2 LED fixtures on my 65 gal planted tank. One is dim-able and the other is not. The are both 36 ins long with several colors and are around 20 watts each.
> Every forum I read, they use T8, T12 etc. But I can't find anything on Par LED lighting
> Could anyone please help me.
> Thanks


All fixtures, LEDs ones especially vary in PAR so the only way to know is to use a PAR reading meter. You can buy these online (kinda expensive) or perhaps you can borrow one from someone local. I would check your local forums, facebook pages, near by hobbyist, etc.


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## oyf709

Single warm/cool white LED should never consider to be efficient enough to grow plants in any shape of form. Just because it looks the same as a CFL or normal T5 and has the indicated color temperature, LED actually peak at a very narrow spectrum. That is another reason why majority of the grow light out there is red and blue instead of white only because the White LED itself doesn't contain enough of either spectrum to promote the good growth of the plants. The only reason why most of people don't run the "perfect" growth LED on aquarium is because it is dame ugly to look at, the purpose of our aquarium are mostly for viewing (except for a few people that growing plants only for business purposes) , so the perfect way is having majority of the white and supplement additional spectrum with red or/and blue LEDs.

PS: When I say LED can't compare to CFL or T5, doesn't mean that are not as good. For those that know me, they know that I am a big LED supporter. T5 and CFL will lose the full spectrum eventually where as LED doesn't deteriorating in that way. when it goes, it burns out entirely but that will take at least 3 to 5 years to happen. The worse case situation for LED is that for Blue LED, (contains small amnt of UV spectrum) will cause the optic of the LED diodes turn brown/black before it burns out. this is mainly due to the nature of the UV spectrum (anything below 450nm)


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