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

[JoshO]

It’s also about respiration of the coral. Zooxanthellae are responsible for coral color and general health. Par levels alone are not the cause for coral health and color. As far as what spectrum does what, no idea. Just offering more to the coral color and growth puzzle.

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Zooxanthellae are quite often in Acropora responsible for up to 90% of the energy needed for calcification! The spectral makeup of a light source will dictate the amount of energy the zooxanthellae can produce.
As for flow, I couldn't agree more in it's importance. I managed to knock a stag over with flow yesterday . But you can have the perfect flow, with too little blue photons and the corals won't grow! (I know the reverse is true also)

 

[tbrown]

I definitely liked the look of my 14000k and 20000k MH more than the 6500k when I ran them back in the day.

 

[JoshO]

I definitely liked the look of my 14000k and 20000k MH more than the 6500k when I ran them back in the day.

Aesthetically it's totally personal preference, I'm very much in the 14k camp! With MH they'll all have high volumes of blue photons, the other wavelengths are what are changed to change the colouration

 

[Reefer Matt]

Zooxanthellae are quite often in Acropora responsible for up to 90% of the energy needed for calcification! The spectral makeup of a light source will dictate the amount of energy the zooxanthellae can produce.
As for flow, I couldn't agree more in it's importance. I managed to knock a stag over with flow yesterday . But you can have the perfect flow, with too little blue photons and the corals won't grow! (I know the reverse is true also)

Yeah, it’s definitely a juggling act. But luckily most coral will adapt. I personally use a ramping spectrum and intensity in my tanks. Toward noon, the light is the most “white” (still like 10-12k), then it tapers to an all blue and violet spectrum toward the end of the night.

 

[HudsonReefer2.0]

I forgot to ask...which MH are you running? I'd wager there's a significant amount of blue photons in there but the amount of other wavelengths is also high which means total energy output is high. I'm going to guess you're not running 250 par, possibly a fair amount higher?

When does the photon become blue? The moment we observe it? lol.

 

[CBonito]

I run my blues all the way up, UV halfway and violets 75 percent in my tank and just mix a little white in as the photoperiod peaks where the sun would typically be right overhead. Set and forget.

 

[JoshO]

When does the photon become blue? The moment we observe it? lol.

The moment it's emitted from it's source. Colour is a reflection for our eyes. But in terms of wavelengths photons will differ in energy. Shining the brightest light at the blackest object will show nothing as all photons will be absorbed and not reflected (I think). As soon as you introduce pigmentation you'll see colour reflected back at you

 

[JoshO]

Yeah, it’s definitely a juggling act. But luckily most coral will adapt. I personally use a ramping spectrum and intensity in my tanks. Toward noon, the light is the most “white” (still like 10-12k), then it tapers to an all blue and violet spectrum toward the end of the night.

Are your blues and violets maxed the whole time during the "white" phase?

 

[MabuyaQ]

That's exactly my point. 200 par really isn't just 200 par. It may be the same number of photons, but the energy in each photon is vastly different. If we graded them 1-10 blue would be around 8, whereas red would only be a 3...that's significantly different in terms of energy! So if we are measuring our tanks by alone, one person's 200 par could be significantly lower in energy than another

Sure let us rate blue light at 8 energypoints. Now what is the use of getting 8 energypoints if you can not use that amount of energy. That energy then has to go somewhere, which in most cases would mean it is converted into heat. In case of corals that could kill them from heatstress. So to prevent that from happening they use another mechanism, they reemit the unused energy as a photon. So corals convert photons from a higher energy level to a lower energy level, which is called fluorescence. So do corals really need, use all that blue light if it mostly increases fluorescence?

 

[Reefer Matt]

Are your blues and violets maxed the whole time during the "white" phase?

No. I use Kessils, which have the Kessil logic that mostly controls spectrum. Violets are 50% during the day. Then go to 100% at night. But I also use ReefBrite xho actinics with them from noon to 6 pm.

 

[ISpeakForTheSeas]

To clarify a few things here:

-PAR (Photosynthetically Active Radiation) technically measures light ranging from 400nm to 700nm (violet to red) - ultraviolet (UV) is below 400, and infrared (IR) is above 700. So, PAR doesn't technically include UV in the reading, but some PAR meters may include a measure of some UV/IR in their measurements.

-Different wavelengths (colors) of light have different amounts of energy in them, but they also have different properties for photosynthesis. Because of this, we absolutely should consider spectrum when using PAR measurements.

-Generally speaking, corals like blue light and dislike red light; white light is a mix of at least red, blue, and green/yellow light - depending on the blend, corals may or may not grow well under it. Whether a coral grows "better" (faster, more resilient, etc.) under white light or blue light is likely dependent on the coral's environment: is the coral from deepwater, or has it been growing under a blue light only tank for a long time now? It'll probably grow better under blue light. Is it from shallow water, or from a tank with whiter lighting? It'll probably grow better under white light.

-White light is best for photosynthesis, and sometimes but not always for coral growth (see my points above); there's more to the picture of coral growth than just photosynthesis.

-Blue light is arguably the most important for corals because that's where Chlorophyll A gets its highest energy peak. Is this because blue light contains more energy, or is it because the organism is better at obtaining what energy is available to it from blue light as opposed to the energy available from other colors? I don't know.

-I've heard that for coral health, red light shouldn't exceed ~15% of the total light spectrum they're under.

-Flow can how the light is bouncing around through the water in the tank; so it may affect PAR both on the macro and micro scales (focusing light in some areas, dispersing it in others, etc.).

-Because each wavelength of light has a different impact on corals (and fish/, but that's a different story), each should be accounted for when looking at PAR. For examples, a light with high blue and high red may not grow corals as well as one with high blue and moderate red. Similarly, a light with high blue and high green may grow corals better than a light with high blue and moderate green. Since the entire spectrum used to grow the coral impacts the coral's health, the entire spectrum should be measured (ideally individually, but that's obviously not always possible for hobbyists).

-Lastly, I don't know if this is an issue for halides and such, but at least for LED's, a ton of companies seem to just flat out makeup a number for their kelvin; I have seen a ton of LED's listed as 6500K that based on spectrum couldn't have been over 5K at the highest.

 

[JoshO]

No. I use Kessils, which have the Kessil logic that mostly controls spectrum. Violets are 50% during the day. Then go to 100% at night. But I also use ReefBrite xho actinics with them from noon to 6 pm.

I'd hazard a guess and say the fact you've got the actinics means you're providing that blue wavelength well whilst allowing whites to give you a more aesthetic look!

 

[JoshO]

Sure let us rate blue light at 8 energypoints. Now what is the use of getting 8 energypoints if you can not use that amount of energy. That energy then has to go somewhere, which in most cases would mean it is converted into heat. In case of corals that could kill them from heatstress. So to prevent that from happening they use another mechanism, they reemit the unused energy as a photon. So corals convert photons from a higher energy level to a lower energy level, which is called fluorescence. So do corals really need, use all that blue light if it mostly increases fluorescence?

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

 

[BeanAnimal]

Let's say we've got 200 par of 420nm (blue) light and on another system we have 200 par of 570nm (yellow) light. From the way the hobby has described par these should equate to the same energy levels, correct? Wrong!!

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.

 

[Reefer Matt]

I'd hazard a guess and say the fact you've got the actinics means you're providing that blue wavelength well whilst allowing whites to give you a more aesthetic look!

Exactly. While the ReefBrites are on, the Kessils are as white as I can get them, with some violet. Then it all ramps to blue from 6-9 pm. Then ramps up similar in the morning. I like some blue for the looks, but don’t like it all the time. The coral grow quick regardless for me though.

 

[BeanAnimal]

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

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).

 

[Lasse]

As the title implies, have we been wrong the whole time about the energy we provide our corals?
I was doing some digging, recently, into journals to better understand what is truly the optimum lighting for Acropora and stumbled across a study which assessed the influence of different Kelvin metal halides on the growth of Acropora Solitaryensis. They studied 5, 10, 15 and 20k temperatures, all with the same PAR value...guess what came out on top? The 20k...the most blue of all the spectrums. I was a little bit baffled by it as we always hear full spectrum is likely to grow corals quicker (anecdotal hobbyist evidence). So I dug a little deeper...here goes.
Light energy is in the form of waves. With the shortest, highest frequency at the UV end of the spectrum and longest lowest at the red end.
PAR is the measurement of the number of photons hitting an area in a given time frame that comes from the range of light which is considered photosynthetically available (I might have worded slightly wrong but hopefully you get the gist). There is no mention of the energy said photons provide, so here is where it gets interesting.
Let's say we've got 200 par of 420nm (blue) light and on another system we have 200 par of 570nm (yellow) light. From the way the hobby has described par these should equate to the same energy levels, correct? Wrong!!
If we go back to what I said earlier about the length and frequency of the light waves then you'll remember that I said blue are shorter and higher frequency. This means that each photon of blue light has more energy than it's friend the yellow photon.
This means that if we base our measurements purely on a par reading, and neglect to factor in spectrum, then we aren't going to be giving our corals the energy we expect!!

Is not as easy as that. The two photosystems involved in photosynthesis - P1 and P2 - need the wavelengths of 700 and 680 nm to work. Shorter wavelengths than 680 needs to be converted to 680 nm by accessory pigments such as carotenoids and phycobilins, which transfer the energy to active part of the photosynthesis. It cost energy. Hence - from here Note the chart



And from here

Sincerely Lasse

 

[JoshO]

To clarify a few things here:

-PAR (Photosynthetically Active Radiation) technically measures light ranging from 400nm to 700nm (violet to red) - ultraviolet (UV) is below 400, and infrared (IR) is above 700. So, PAR doesn't technically include UV in the reading, but some PAR meters may include a measure of some UV/IR in their measurements.

-Different wavelengths (colors) of light have different amounts of energy in them, but they also have different properties for photosynthesis. Because of this, we absolutely should consider spectrum when using PAR measurements.

-Generally speaking, corals like blue light and dislike red light; white light is a mix of at least red, blue, and green/yellow light - depending on the blend, corals may or may not grow well under it. Whether a coral grows "better" (faster, more resilient, etc.) under white light or blue light is likely dependent on the coral's environment: is the coral from deepwater, or has it been growing under a blue light only tank for a long time now? It'll probably grow better under blue light. Is it from shallow water, or from a tank with whiter lighting? It'll probably grow better under white light.

-White light is best for photosynthesis, and sometimes but not always for coral growth (see my points above); there's more to the picture of coral growth than just photosynthesis.

-Blue light is arguably the most important for corals because that's where Chlorophyll A gets its highest energy peak. Is this because blue light contains more energy, or is it because the organism is better at obtaining what energy is available to it from blue light as opposed to the energy available from other colors? I don't know.

-I've heard that for coral health, red light shouldn't exceed ~15% of the total light spectrum they're under.

-Flow can how the light is bouncing around through the water in the tank; so it may affect PAR both on the macro and micro scales (focusing light in some areas, dispersing it in others, etc.).

-Because each wavelength of light has a different impact on corals (and fish/, but that's a different story), each should be accounted for when looking at PAR. For examples, a light with high blue and high red may not grow corals as well as one with high blue and moderate red. Similarly, a light with high blue and high green may grow corals better than a light with high blue and moderate green. Since the entire spectrum used to grow the coral impacts the coral's health, the entire spectrum should be measured (ideally individually, but that's obviously not always possible for hobbyists).

-Lastly, I don't know if this is an issue for halides and such, but at least for LED's, a ton of companies seem to just flat out makeup a number for their kelvin; I have seen a ton of LED's listed as 6500K that based on spectrum couldn't have been over 5K at the highest.

- "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

 

[Lasse]

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

Sincerely Lasse

 

[BeanAnimal]

Is not as easy as that. The two photosystems involved in photosynthesis - P1 and P2 - need the wavelengths of 700 and 680 nm to work. Shorter wavelengths than 680 needs to be converted to 680 nm by accessory pigments such as carotenoids and phycobilins, which transfer the energy to chlorophyll molecules. It cost energy. Hence - from here Note the chart

Sincerely Lasse

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.