Estimating PAR from wattage

[BeanAnimal]

Your right not many people have a par meter, but I can guarantee you every single one is trying to estimate to some extent how much their lights are outputting......

As useful as estimating the number of blue jellybeans in opaque jar...

Your making it sounds light par is some sort of imaginary thing we all came together to make up?

Not even close. I am saying that it is a real measurement that has very little real world meaning in the manner in which it is almost universally accepted and applied in this hobby.

Different corals need different amounts of light.....PAR seems to be the easiest way to measure this?

Until you realize what "PAR" is actually measuring and understand that it is the wrong thing to be measuring. Explained above. It is similar to trying to discern the health of a diet based on the calorie count, not the content of what makes up those calories, but even worse, as we don't know what content (specific spectrum) that coral in general, let alone a given coral need.

If i put an acro at the bottom of my tank in the shade its going to die....if i put an acan on the top of a rock being blasted its going to die.

And you don't need a "PAR" meter to tell you that. Nor does the number "123" mean that the acro will live or die. It may thrive at 123 PPFD of optimum spectrum and wither at 223 PPFD of sub-optimal spectrum. It may thrive under both, but take on wholly different pigmentation or structure under both. "PAR" does not tell you any of this. It is a "feel good" number from a tool that people think is important, for whatever misguided reason that has spread like wildfire through this hobby over the last several years.

 

[BeanAnimal]

dang we got Butter Bean in here swinging for the fences.

I think you probably could come up with napkin math PAR estimates based off of wattage, light spread, depth and color mix pretty easily. Dunno about bring within 2 PAR but I think ballpark is possible.

I would say, given the vast number of variables that you wont even be "ballpark".

As i said, even with datasheets in hand for the emitters, circuit topology and lens spread and a page full of very accurate calculations, you be lucky to be "ballpark" to real world measured output, as there are still a good number of variables and fudge factors.

Now, how useful that would actually be to a reefer I dunno - PAR is just one small part of a complex set of variables that determine coral health and so is a loose PAR number guess really helping or hindering the troubleshooting process?

In general, it is hard to have too much light (within reason). Burned tips... move things down... browning out... move them up. Acclimation to a new light (spectrum and intensity) is rather important for some corals.

Spectrum is very important. Given 10 tanks, with the same exact coral and 10 different fixtures tuned to 10 different spectrums -- but all the SAME "PAR".... you will have 10 different outcomes.

 

[oreo54]

Well this thread is fun...
As mentioned the biggest issue is caused by various designs.
Mostly beam geometry and brand efficacy.

In the fw world I attempted to come up with a " rule of thumb" for those without par meters. Which was pretty much everyone

Using a few dozen on line par measurements ( with if course each having their own possible errors" I came up with a fairly reasonable estimate that was " workable"
1w = 1par @ 18"
The parameters were .2-1 w class LEDs that were lensed at 120 degrees

Pretty narrow parameters in comparison to most reef lighting
The small size of the emitters tended to a general efficacy across light brands .
Like household LEDs generally hover over 110 lumens per watt

And since royal blue emitters were the base for whites both whites and blue had approx same efficiency in terms of par/watt.
You cannot use lumens since each color has a different conversion .
Equal amount of blue photons would ensure very low lumens yet have the same par as a white led.

Interesting enough Tuillio mentioned using old school watts as a measuring stick.
Don't ask me to find it though.

Oh and the spread of my data was like .95 par/watt to ( an outlier) of 1.6.
So 1 to 1.2 was my compromise.
I asked others to add eaea but got no response.

So no no "within 2 par" accuracy but useable on a general scale.

Along with that is another hypothesis that light behaves more linear by depth than logrythmic.
100 par at 12" us likely to be somewhere around 50 par at 24" than 25 par .

So between 60 to 120 degree beam angles and " egg" LEDs to better bin Cree/ luxeons I certainly wouldn't bet on 2 par accuracy.

Didn't even mention things like hanging height differences, screen/ glass/ no tops. Painted glass ect.
Or the "par doesn't matter" school...

For proof some mathmatically inclined one could gather all the manuf. data, normalize
to a specific height and calculate the statistics of the data to see what it looks like.
There is a lot of user data but since most do not run their lights at 100% with all channels it would be a mess...

In the fw world most users measured lights at 100% simplifying life.

 

[BeanAnimal]

As mentioned the biggest issue is caused by various designs....

...For proof some mathmatically inclined

Longhand for "there is no reasonable way to estimate 'PAR' from the wattage of a mixed reef luminaire -- even if doing so provided some meaningful number :)

 

[oreo54]

https://reefs.com/magazine/ecotech-radion-pro-aqua-illumination-hydra-ghl-mitras-6100hv-and-6200hv/
Food for thought..

 

[strich]

And you don't need a "PAR" meter to tell you that. Nor does the number "123" mean that the acro will live or die. It may thrive at 123 PPFD of optimum spectrum and wither at 223 PPFD of sub-optimal spectrum. It may thrive under both, but take on wholly different pigmentation or structure under both. "PAR" does not tell you any of this. It is a "feel good" number from a tool that people think is important, for whatever misguided reason that has spread like wildfire through this hobby over the last several years.

You're right that PAR alone doesn't guarantee coral health, and spectrum matters a lot especially for things like pigmentation and growth form. But dismissing PAR entirely is misleading and frankly unhelpful to the discussion.

PAR isn’t a "feel good" number - it's a baseline. It tells you how much usable light is reaching the coral, which is essential for photosynthesis. It doesn’t capture spectral quality, but without knowing intensity, you're flying blind, especially with high-light species like acros.

Think of PAR like a speedometer. It doesn’t tell you how good your engine is (spectrum), or how smooth the road is (water quality), but you still need to know how fast you’re going.

Optimal coral health comes from both PAR and spectrum - not one or the other.

 

[fish_collector]

Good conversation from all contributing parties.

I grow only SPS and some clams. I have an Apogee PAR meter that I've used to measure the PAR in different parts of my tank. I have found it comes in handy when I need to move something for whatever the reason, or when I add a coral. There are locations in my tank, a shallow frag tank, that vary wildly in PAR. I've found it easier to know what the particular PAR is at a given location than to blindly put a coral in and have it bleached by the next afternoon. I'm active in my local reef club and routinely add corals from other member's tanks, a lot of our members have PAR meters also and share that info when we trade them, it's much better to acclimate a new coral in the same PAR as it had been growing. I'm not a scientist and have no idea how a PAR meter works, it counts photons I suppose, but I do feel they work for their intended purpose and are beneficial to reef aquarists for the reasons I've mentioned.

And again, thanks to all who've contributed, a one sided argument is no fun at all. That's all I've got to say. Keep on reefing on.

 

[fish_collector]

I was thinking about this for a few moments and I do have something to add, and please someone correct me if I’m wrong. Let’s say for the sake of argument a PAR meter counts photons, if I have a reading of 300 at the frag rack under my mixed color LED, that means I’m measuring all of the spectrum available at the sensor at that location and the value is 300, if I move to another location and I measure 150 or 450 or whatever, that is the amount of light at that given location. Now, I understand some wavelengths of light are more useful than others to coral, and a PAR meter doesn’t differentiate spectrum but rather gives a measure of light intensity where the sensor is. If it’s all blue or all white or whatever, it measures the intensity. It’s not even valid to assume white light has more PAR than blue because it doesn’t, it’s just how our eyes perceive it. So one must take that into consideration when using the value a PAR meter gives you. I might even go further to say a PAR meter may be more useful as a guide in 1 tank and not necessarily from tank to tank with different lighting. But, a PAR meter does measure light intensity and I believe knowing that is better than guessing.

I don’t believe it’s possible to estimate PAR even if you know the wattage, there are too many variables.

 

[fish_collector]

I would say, given the vast number of variables that you wont even be "ballpark".

As i said, even with datasheets in hand for the emitters, circuit topology and lens spread and a page full of very accurate calculations, you be lucky to be "ballpark" to real world measured output, as there are still a good number of variables and fudge factors.



In general, it is hard to have too much light (within reason). Burned tips... move things down... browning out... move them up. Acclimation to a new light (spectrum and intensity) is rather important for some corals.

Spectrum is very important. Given 10 tanks, with the same exact coral and 10 different fixtures tuned to 10 different spectrums -- but all the SAME "PAR".... you will have 10 different outcomes.

Agreed.

Perhaps a PAR meter should be a tool that we use along with other pieces of info/data that we gather to make decisions. It does give us useful info but as Bean points out it does not take into consideration the spectrum, it’s useful it’s just not the whole picture. I think that’s the point Bean is trying to make here.

 

[VintageReefer]

I was thinking about this for a few moments and I do have something to add, and please someone correct me if I’m wrong. Let’s say for the sake of argument a PAR meter counts photons, if I have a reading of 300 at the frag rack under my mixed color LED, that means I’m measuring all of the spectrum available at the sensor at that location and the value is 300, if I move to another location and I measure 150 or 450 or whatever, that is the amount of light at that given location. Now, I understand some wavelengths of light are more useful than others to coral, and a PAR meter doesn’t differentiate spectrum but rather gives a measure of light intensity where the sensor is. If it’s all blue or all white or whatever, it measures the intensity.

The Vabira shows par levels for RGB then gives total par at the bottom

It’s not even valid to assume white light has more PAR than blue because it doesn’t, it’s just how our eyes perceive it. So one must take that into consideration when using the value a PAR meter gives you. I might even go further to say a PAR meter may be more useful as a guide in 1 tank and not necessarily from tank to tank with different lighting. But, a PAR meter does measure light intensity and I believe knowing that is better than guessing.

I don’t believe it’s possible to estimate PAR even if you know the wattage, there are too many variables.

No arguments from my side

 

[MikeReefs]

Chat GBT your lights and tank specs and input your intensity/ light height. Believe it or not it’s a good “estimate” it’ll tell you par ranges high med and low/sandbed. Seen a video of someone with the same tank and lights and schedule as mine and he got similar results

 

[BeanAnimal]

But dismissing PAR entirely is misleading and frankly unhelpful to the discussion.

PAR meters — and the weight people put on their readings... are what’s misleading.

You say it’s a baseline, but a baseline against what?

PAR only counts photons in the 400–700nm range, but corals only use a subset of that — and which subset they respond to depends on species, depth, and morphology. Which subset is present differs drastically between fixtures and user settings. Not all "usable light" is used equally and every fixture and setting presents a different blend of "usable light"

Given that every light source and configuration produces a different spectrum, what are we actually comparing?
Two tanks might both measure 300 PAR, but their spectral peaks and flux distributions will be completely different.

What looks "close" on a spectral graph to the human eye can be worlds apart in actual spectral energy delivery.


I measured 300 "PAR" (it is PPFD btw) is like saying:
“We both have a gallon of Kool-Aid, so they must be equal.”
We don’t choose Kool-Aid by container size, we choose by flavor and not all flavors are as favorable or consumed at the same rate.

So sure — PAR is a number. But it lacks meaningful context and functions mostly as a comfort metric.

You’re not flying blind without it -- You’re blind if you think it tells you anything beyond rough relative brightness in the 400–700nm range. And for that? A $10 lux meter would do about the same job.

But even then, back to the simple reality that you would be hard pressed to have too much light if you equip your tank within any reasonable metric and more light is generally better if common sense is used. The top has more light than the bottom. . You don't place low light corals at the top and you don't place high light corals at the bottom. No meter needed. Countless thousands (millions) if successful reef tanks are stocked off of this premise without a meter. The meter does not add an actual useable metric to this process, even if most people are mislead to think it does.

 

[Danjoethepirate]

what exactly becomes meaningless? The number that we are using to measure PAR?

I think my post speaks for itself. What part (honestly) are you not clear on? I will be more than happy to elaborate.

Obviously PAR is not as simple as many think but measuring a number is still important in keeping coral.

IMHO and given fact (not reefing lore or common practice) measuring "PAR" is not an "important" part of keeping coral. There have been countless thousands (tens, hundreds, millions) of successful reef tanks that have never seen a "PAR" meter. The tool and its output are almost universally misunderstood by the vast majority of those in this hobby that think they are using it to some meaningful end.

The irony is that PAR tells you nothing about spectral quality, distribution across the tank, or how a given coral actually uses the light it's exposed to. It’s like measuring all calories as equal -- technically a number, but practically meaningless if you don’t know whether it’s from sugar, protein, or alcohol. -- the fat, carbs, or protein -- let alone the subsets of those and their ramifications on every aspect of health and bioavailability.

Well, this thread could have been decent with good conversation but someone left the bean dip out overnight and it turned rancid

Sometimes nonsense is best stopped in it's tracks. Ignoring the conversation about the actual usefulness of PAR measurements or their accuracy themselves. Let's just say "PAR" Is the most important thing in the world, for the sake of argument...

There is just no (even remotely) reasonable way to even come close to estimating par by looking at the wattage of a fixture.

Sure - one could could:

1 - Count the emitters.
2 - Look up the BRAND and TYPE and BIN of each one, recording its maximum luminous efficacy.
3 - Do the math, based on the datahsheet wavelength(s) of each emitter, to find its maximum Flux at 100% output.
4 - Assume that all emitters are running at 100% output with no thermal throttling (they don't run this way)
5 - multiply by some driver and power supply efficiency
6 - multiply by some arbitrary lens coefficient at some arbitrary distance

And get an extremely rough estimation of "PAR" (PPFD) at 100% output in a perfect world. And even that number will be:

1 - insanely ballpark (wildly off) due to the number of variables.
2 - derived by an exercise that takes a tremendous amount of work and math.

So there is NO WAY that "he" or anybody is going to come close to a "PAR" estimate by looking at a mixed emitter LED fixture. The notion is patently ridiculous and anybody who puts forth otherwise has absolutely no clue what they are talking about. There is no conversation to be had, it is a non starter.

The bean dip is not sour... bean dip is never good.

Hey.....if you put bacon in bean dip, it is A-ok!

 

[BeanAnimal]

Hey.....if you put bacon in bean dip, it is A-ok!

There is no bean dip that is A-ok, but that is my opinion that has no supporting physics or biology to substantiate it :)

 

[Borat]

very easy 1 watt is exactly one par (this is bloody obvious!) so if you want 500 pars, buy a 500 wat light

 

[VintageReefer]

There is no bean dip that is A-ok, but that is my opinion that has no supporting physics or biology to substantiate it :)

Is it a multi layer dip, with a layer of guacamole, separated by a layer of cheese and sour cream?

 

[VintageReefer]

very easy 1 watt is exactly one par, so if you want 500 pars, buy a 500 wat light

Wrong.

Every 1$ = 1 Par unit.

The more monies the light, the more par units it can make. Do not buy on sale, those are defect units that output less par units. Only fool buy light on sale. 15% off = 15% less par

 

[BeanAnimal]

Wrong.

Every 1$ = 1 Par unit.

The more monies the light, the more par units it can make. Do not buy on sale, those are defect units that output less par units. Only fool buy light on sale. 15% off = 15% less par

So I am confused was the Solaris more or less "PAR" then? Sure were a lot of arguments back in the day, maybe we can finally get it cleared up.

I mean -- that is where most of this nonsense got started... Well that and Sanjay's absolutely amazing (and arguably extremely successful) attempt to spectral plot and catalog every MH lamp (and reflector) that he could get his hands on.

 

[VintageReefer]

So I am confused was the Solaris more or less "PAR" then? Sure were a lot of arguments back in the day, maybe we can finally get it cleared up.

I mean -- that is where most of this nonsense got started... Well that and Sanjay's absolutely amazing (and arguably extremely successful) attempt to spectral plot and catalog every MH lamp (and reflector) that he could get his hands on.

In old days, led was strong, and well made, and rightfully expensive. As time goes on, they become cheaper, and crappier! Just like automobile. 100k on suv and inside is plastic and cheap!

 

[Borat]

Wrong.

Every 1$ = 1 Par unit.

The more monies the light, the more par units it can make. Do not buy on sale, those are defect units that output less par units. Only fool buy light on sale. 15% off = 15% less par

But $1 = 1wat, thus 1$ =1 par, this is another obvious thing!