Have we been wrong in our understanding of PAR this whole time??

[Reefer Matt]

Because the hobby is fraught with viral misunderstanding that turns into viral misinformation that becomes gospel.

PAR meters are one of the most misunderstood and misused tools in this hobby. Everyone runs around quoting PAR numbers and telling everyone else how indispensable PAR meters are. It is laughable at best. PAR readings can give you a better ballpark than the eye and a measurable reference between two fixtures with the SAME spectral output. Comparing two fixtures with different spectral output, or what some other internet user measured on their tank that they said is perfect for coral? No, it is pointless. You really tell much without spectral information and to that end very few people in this hobby are equipped to interpret spectral plots or comparisons, let alone measure them.

But wait... there's more.

Even if you COULD measure PAR and know EXACTLY what it meant. What is the TARGET value? Where does that come from? Moreover, every spot in your aquarium likely has different readings, different spectral properties due to reflection, refraction, shadowing, etc. So what is the perfect spot and how does the coral growing out of that spot (and shadowing other spots) change things.

PAR meters are useful in a ballpark sense. Look I have somewhere between 50 and 100 PAR on the bottom and somewhere between 300 and 500 par near that top. That is pretty much ALL they are good for. The rest is made up hokum that people pretend to be precision importance.

I agree that there is no perfect value for par and certain coral to adhere to, and rather, a range is more sufficient. To me, a best guess is better than no clue when it comes to providing an environment for animals to live in. I find a par meter invaluable in preventing unnecessary coral death in my situation. Maybe someone with 20-30+ years experience doesn’t need a par meter, but for us average Reefers, it has its uses, imo.

 

[Lavey29]

I run phoniex 14k it’s got blues for sure.. my par is 1000 under the water line and around 400-600 on rocks and 250 in the sand.

You must have a nice tan too

 

[BeanAnimal]

- "White" light is very much personal interpretation in my opinion. Some will say that 14k looks white to them, whilst others will say it's very blue still (I'm in the bluer camp)
- With regards to "white" being better for photosynthesis, this again is very much down to the source of light and it's spectral makeup, par would also be important here as long as we know the spectrum.
- The whole spectrum might be used in some aspect, but the volume that each wavelength is utilised will differ greatly (basically what you're saying about blue being used a lot and the others not so much)
- My main point with this is that the majority of hobbyists probably aren't away of these factors when setting up an LED fixture, which is why many struggle. The reason MH and T5 work so well at all the temperatures is because the lower nm ranges never change, only the high nm are reduced to give the bluer colour (that's my understanding) so the energy will always be there. If you only run blues at 50% on a radion then you may not be providing the right energy based off par alone

Your eye is a crude instrument. "White light" is misleading. "full spectrum" is also misleading to an extent.

Please look up the term "metamerism".

Your main point (even if derived from a slight misunderstanding) is valid. PAR meters are not what people think they are or used in a way as meaningful as people think that they are.

 

[BeanAnimal]

I agree that there is no perfect value for par and certain coral to adhere to, and rather, a range is more sufficient. To me, a best guess is better than no clue when it comes to providing an environment for animals to live in. I find a par meter invaluable in preventing unnecessary coral death in my situation. Maybe someone with 20-30+ years experience doesn’t need a par meter, but for us average Reefers, it has its uses, imo.

I think it is a great ballpark tool. Nothing more.

 

[Lasse]

This is good

If You're Serious About Lighting, Know This

Per @GoVols suggestion: Lighting for reef aquaria can be as simple or complex as you wish to make it. If you’re really serious about lighting, these are some of the terms you might want to be familiar with: Accessory Pigment: A photopigment that absorbs light and transfers it to chlorophyll a...

www.reef2reef.com

Sincerely Lasse

 

[BeanAnimal]

You must have a nice tan too

I think the phoenix 14K were one of my favorite all time DE bulbs. The Radiums were nice too...

 

[tbrown]

You must have a nice tan too

He lives in Vegas, of course he has a nice tan!

 

[JoshO]

Yes - anything not reflected is absorbed as energy, usually in the form of heat. Of course you can get motion as well (the classic solar windmill for example).

I don't think there's any real risk of this with LEDs. Temperature of water is very manageable in this hobby for the volumes of light energy we use

 

[JoshO]

PAR definition says between 400 and 700 nm. UV wavelengths is below 400 nm - not included in PAR

Sincerely Lasse

I very much agree with both of your replies. In a way you're backing what I've maybe misworded. My point is very much about the efficacy of spectrums created on LED fixtures. I maybe should have clarified this from the off! It's very easy for a hobbyist to put a par meter in the middle of their tank and slide "all channels" up to the desired PAR they've been recommended. But that measurement will not be emitting the same energy as if they moved only blue and a small amount of red up to the point where the same par is achieved. Full spectrum MH bulbs will have an abundance of all the wavelengths that will provide incredible results, an LED light set at the same colour temperature will absolutely not do that.
There needs to be a much greater emphasis on the importance of wavelengths for new hobbyists so they understand what they're trying to achieve when lighting their systems

 

[BeanAnimal]

I don't think there's any real risk of this with LEDs. Temperature of water is very manageable in this hobby for the volumes of light energy we use

The response was not in context to manageability, I simply answered your question. However, Some light sources (Metal Halide) for example have a high IR emittance that that is significant compared to a comparable source with low IR emittance ( a typical reef LED fixture). The water heating (both direct and from objects touching or in the water that absorb the IR) is very significant for the MH.

 

[JoshO]

And to that end - think it is even more complicated with coral (and less understood) than it is with terrestrial plants. There is also significant Stokes shift responsible for changing emissivity from lower wavelength to higher wavelengths.

PAR meters are cool - but not the precise coral light meters that people make them out to be or want them to be.

That last paragraph is precisely my point!

 

[JoshO]

The response was not in context to manageability, I simply answered your question. However, Some light sources (Metal Halide) for example have a high IR emittance that that is significant compared to a comparable source with low IR emittance ( a typical reef LED fixture). The water heating (both direct and from objects touching or in the water that absorb the IR) is very significant for the MH.

Your initial response wasn't relative to the point being made in this thread. We aren't talking about levels of light that will heat our tanks beyond the capability of coral survival, simply that par measurements are not as accurate a measurement of energy provided without understanding spectrum

 

[BeanAnimal]

That last paragraph is precisely my point!

Yep - kinda been my rant for a long time. However, it falls mostly upon deaf ears. People want to have magic tools, so they have magic tools.

 

[Lasse]

But that measurement will not be emitting the same energy as if they moved only blue and a small amount of red up to the point where the same par is achieved.

Read my links again - this is not true

Sincerely Lasse

 

[BeanAnimal]

Your initial response wasn't relative to the point being made in this thread. We aren't talking about levels of light that will heat our tanks beyond the capability of coral survival, simply that par measurements are not as accurate a measurement of energy provided without understanding spectrum

No - you lost track of the context of the response and your own words. I did not. Again, I responded to that thing that you typed (rhetorical or not) that ended with a question mark (screenshot below for clarity). No more, No less. there was no implied context, misunderstanding, lost point or tangent.

You further responded that said "heat" was manageable and not significant and not the subject. I think you kinda of got lost.

Of course manageability of the heat was not the point, and I responded as such, but did point out (AGAIN IN REFERENCE TO YOUR ORIGINAL QUOTE) that there is certainly a difference in heating between different wavelengths. Simple conversation.

In any case, let's just move on. An argument here is pointless. In fact, I think I will see my way out of the thread before others get heated.

 

[JoshO]

Because the hobby is fraught with viral misunderstanding that turns into viral misinformation that becomes gospel.

PAR meters are one of the most misunderstood and misused tools in this hobby. Everyone runs around quoting PAR numbers and telling everyone else how indispensable PAR meters are. It is laughable at best. PAR readings can give you a better ballpark than the eye and a measurable reference between two fixtures with the SAME spectral output. Comparing two fixtures with different spectral output, or what some other internet user measured on their tank that they said is perfect for coral? No, it is pointless. You really tell much without spectral information and to that end very few people in this hobby are equipped to interpret spectral plots or comparisons, let alone measure them.

But wait... there's more.

Even if you COULD measure PAR and know EXACTLY what it meant. What is the TARGET value? Where does that come from? Moreover, every spot in your aquarium likely has different readings, different spectral properties due to reflection, refraction, shadowing, etc. So what is the perfect spot and how does the coral growing out of that spot (and shadowing other spots) change things.

PAR meters are useful in a ballpark sense. Look I have somewhere between 50 and 100 PAR on the bottom and somewhere between 300 and 500 par near that top. That is pretty much ALL they are good for. The rest is made up hokum that people pretend to be precision importance.

I apologise I totally missed this! I think, from the studies I've read, that we need to focus on the wavelengths of light that corals utilise most. There are studies out there that do look into this. Find the relevant par levels for the different corals with these wavelengths and go from there. I admit there is a ton of work to be done, but it is doable, and would likely result in a wider success across the hobby.

 

[MabuyaQ]

I just want to clarify before responding, are you saying the unused energy will heat the water?

Can't change the laws of physics, if you absorp the photon like you say you absorp the energy. Any and all of that energy that is not used has to go somewhere. The simplest way to get rid of it is releasing it as heat. Since corals are very sensitive to heat, that isn't the best solution. The mechanism they therefore use is converting it back in a photon and releasing it. Now the question is, is increasing this fluorescence by adding more blue spectrum really helping the coral?
Like Lasse said the actual photo reactive center found in chlorophyll contains a primairy pigment p680 or p700 (p=pigment and the 680 and 700 stand for the nm of light of the photon that is directly converted in an electron by this pigment, so red light). That electron is what is passed on for the chemical reaction. Directly attached to this photo reactive center is a secondairy pigment that absorps light in the 400nm to 500nm range (so blue light) to create an electron that is passed on, so transported to the primairy pigment. Like any and all kind of transport there is some kind of loss/inefficiency. All other pigments found in corals that use light at different wavelentgths are attached to this photo reactive system and therefore the electrons created also need to be transported along a longer pathway probably incuring greater losses than even that of the blue absorption pigment.
Red light of the right wavelength is therefore most efficient and in theory all corals need if you provide the right amount, it would make them really ugly. All flesh would be transparent so you would see nothing but white skeleton except for a minimum amount of brown zoõxanthellae. Don't think they would be very healthy though under such unnatural conditions. The major problem with red spectrum light is that there really isn't any much room for fluorescence if you get to much of it, so the only option left may be trying to survive the heatstress. Which corals are bad at.

 

[JoshO]

No - you lost track of the context of the response and your own words. I did not. Again, I responded to that thing that you typed (rhetorical or not) that ended with a question mark (screenshot below for clarity). No more, No less. there was no implied context, misunderstanding, lost point or tangent.

You further responded that said "heat" was manageable and not significant and not the subject. I think you kinda of got lost.

Of course manageability of the heat was not the point, and I responded as such, but did point out (AGAIN IN REFERENCE TO YOUR ORIGINAL QUOTE) that there is certainly a difference in heating between different wavelengths. Simple conversation.

In any case, let's just move on. An argument here is pointless. In fact, I think I will see my way out of the thread before others get heated.

The screenshot response was not rhetorical, I was trying to understand the context of the commenters statement. It bore no relevance to the statement I was making in that simply measuring par without understanding spectrum is a bad way of doing things as it's very inaccurate. I'm not disputing unused light energy will create heat, but absolutely a different subject to the one I'm bringing to the table.

 

[tbrown]

Yep - kinda been my rant for a long time. However, it falls mostly upon deaf ears. People want to have magic tools, so they have magic tools.

Where can I get these magic tools???

 

[MabuyaQ]

I don't think there's any real risk of this with LEDs. Temperature of water is very manageable in this hobby for the volumes of light energy we use

Temperature of water is manageable for you but you can not assume that this means the internal temperature in the coral is manageable for the coral.