Is white light necessary in a reef?

[dball711]

Not sure I follow your example 1 PAR of blue vs 300 PAR of white, of course the white wins in that example. If winning is measured by usable PAR.

if you consider 300 PAR of both (blue at 100% PUR, White at 80% PUR) then blue wins with 300 PAR vs 240 PAR for the whites right?

 

[Eric_n_Ga]

White light dilutes the PUR ? Is that to our eye or to the photosynthetic organisms ? That would mean it's diluting the spectrum? This is way over my head

 

[NanCrab]

White light dilutes the PUR ? Is that to our eye or to the photosynthetic organisms ? That would mean it's diluting the spectrum? This is way over my head

It’s WAAAY over my head!!!!

 

[YoungReefer10g]

you lost me at not sure lol

 

[ActiveAngel]

Not sure I follow your example 1 PAR of blue vs 300 PAR of white, of course the white wins in that example. If winning is measured by usable PAR.

if you consider 300 PAR of both (blue at 100% PUR, White at 80% PUR) then blue wins with 300 PAR vs 240 PAR for the whites right?

No worries. I can elaborate. Note that the following example is simplified.

In this example, let’s say your overall PAR is 300 of white light at 80% . This would mean your PUR is 240.

Compared to 240 overall PAR of blue light at 100%. This would yield a PUR of 240.

So both of these examples have the same PUR. However, the blue is using less energy... because it’s overall PAR is less.

*again, simplified example.

 

[ActiveAngel]

So if we have blues turned on and they’re giving 240 PAR on their own. But then we turn on whites... hypothetically, if 0% of the white is useful (which we know is untrue), and the PAR increases to 300... then we would know this meter would read 80%.... and this worst case scenario has a PUR of still 240. It didn’t change.

But because white light includes blue, we already know that more than 0% of light From the white LEDs is usable. Let’s say that it’s 50% for the second example. If the PAR reading is 300... then (300-240) x 50% = an increase of 30 PUR. So 270 PUR

This is why adding white light cannot decrease PUR. Conceptually, it can either increase or stay the same. And because white includes blue, we can conclude it won’t stay the same. So it must increase PUR.

It’s “efficiency” will decrease, but it’s “sufficiency” will increase, in terms of delivering energy to corals.

 

[Steve Burton]

Got it, increasing white light does decrease the PUR percentage of total light, not the total PUR.

 

[Eric_n_Ga]

%. Ahhhh

 

[ActiveAngel]

Got it, increasing white light does decrease the PUR percentage of total light, not the total PUR.

Exactly!

PUR - Usable radiation
PAR - Active Radiation
Usable is a subsection of Active.

 

[dball711]

And my point of PUR dropping is valid. While the PAR will increase, the overall % of usable PAR (PUR) is a lower value.

"But because white light includes blue, we already know that more than 0% of light From the white LEDs is usable. Let’s say that it’s 50% for the second example. If the PAR reading is 300... then (300-240) x 50% = an increase of 30 PUR. So 270 PUR"

Respectivly, I'll disagree with this analogy. Adding the white light will increase PAR and the PUR by % of the PAR.

 

[Eric_n_Ga]

So par goes up , pur goes up , pur %goes down , but corals dont use white light ? Or don't need white light ? So it's measuring available usable radiation . But what the use of increasing the PUR with PAR by adding white if the corals don't need it anyway ?

 

[ActiveAngel]

And my point of PUR dropping is valid. While the PAR will increase, the overall % of usable PAR (PUR) is a lower value.

"But because white light includes blue, we already know that more than 0% of light From the white LEDs is usable. Let’s say that it’s 50% for the second example. If the PAR reading is 300... then (300-240) x 50% = an increase of 30 PUR. So 270 PUR"

Respectivly, I'll disagree with this analogy. Adding the white light will increase PAR and the PUR by % of the PAR.

Except PUR doesn’t drop, it must increase, as in the proof above.

By analogy, If we have a bag of 100% red gummy bears, and a picky child that only likes red ones and ignores other colors. And then we buy a Variety bag of gummy bear and add it to the bowl of red ones. Then the number of red gummy bears increases; even though the percentage of red ones goes below 100%. Yes, some colors get ignored (I.e. wasted energy), but the amount used as a food source (I.e. usable energy) increases.

 

[dball711]

PUR as a percentage drops as the PAR value increases when adding more white light energy (outside the blue spectrum).

In a real world example, the charts below show the point I'm making...


First reading shows results with NO whites 1215 PAR with PUR @ 78% = usable PAR is 947

Second reading shows the same light fixture with whites added 1333 PAR but PUR drops 2% to 76% = usable PAR is 1013

In this real life example the addition of whites causes a 2% drop in PUR% with an increase of 66 to the usable PAR. PAR is increased while the PUR % drops.

I'm not

 

[ActiveAngel]

PUR as a percentage drops as the PAR value increases when adding more white light energy (outside the blue spectrum).
View attachment 24073
In a real world example, the charts below show the point I'm making...
View attachment 24074

First reading shows results with NO whites 1215 PAR with PUR @ 78% = usable PAR is 947

Second reading shows the same light fixture with whites added 1333 PAR but PUR drops 2% to 76% = usable PAR is 1013

In this real life example the addition of whites causes a 2% drop in PUR% with an increase of 66 to the usable PAR. PAR is increased while the PUR % drops.

I'm not

Exactly right. You got it!

 

[bigd]

I digress!


D

 

[ActiveAngel]

So par goes up , pur goes up , pur %goes down , but corals dont use white light ? Or don't need white light ? So it's measuring available usable radiation . But what the use of increasing the PUR with PAR by adding white if the corals don't need it anyway ?

Good question, and it’s not exactly true that corals don’t use white light. They do.

But it’s important to note that white light is composed of many colors, including blues... this alone indicates that those corals and algaes that use blue light, will also use white light.

The big question at the root of this thread, is how useful are the other wavelengths (I.e. the reds, greens...) that compose white light. Many corals do quite well in captivity with all blues. But how much better would they do if they had access to other wavelengths? Would some of these other wavelengths provide a benefit comparable to vitamins or micronutrients, macronutrients, or maybe no benefit? Obviously, you can’t have your cake and eat it too, as they say. Additionally, it likely isn’t fair to generalize what is good for 1 species is good for all species. But we can make educated guesses, observe effects, and do our best to provide a good home!

IMO, it’s much harder to prove that the other wavelengths in white light aren’t beneficial, than to prove that they are. I’m sure there are some scientific papers on it... and I’ll definitely be looking into it down the road out of my own curiosity.

 

[dball711]

This may well be one of the best threads started in a while. There's a lot of consideration to be taken into consideration around lighting in or aquariums. With more light sensors and light sensor features we can take a much closer look at lighting in our aquariums. Just looking a PAR is only one side of the coin (PUR) usable (good/bad) spectrum should also be taken into consideration. The amount of white light we use is all about personal preference right, or is it...

First,

Exactly right. You got it!

Andrew, thanks for your vote of confirmation but I think more accurately "you (Andrew) got it, this is what I've saying all along"

Second,

So par goes up , pur goes up , pur %goes down , but corals dont use white light ? Or don't need white light ? So it's measuring available usable radiation . But what the use of increasing the PUR with PAR by adding white if the corals don't need it anyway ?

The first part of this statement "So par goes up , pur goes up, pur %goes down" is not accurate. As PAR increases/decreases then PUR% can also increase/decrease. PUR, the usable portion (percentage of PAR) can also be described as a measure of the photosynthetically available radiant energy (PAR). PUR is simply a measure of the photosynthetically useful part of a light spectrum.

The Second part of this statement "but corals dont use white light ? Or don't need white light ?" Can be explained in the example below...

The graph below is taken from a tank with a full spectrum (mostly white light). Notice the colourful part of the graph shows the useful (photosynthetically useful) part of the light spectrum, the thick black line shows the "actual" spectrum of the light fixture. There is a good deal of light that is not in the usable spectrum, the PUR value in this example is 64% meaning 64% of the PAR is photosynthetically usable energy.



Next look at example of a tank with all blue lights, no whites. See how the thick black line matches more closely the photosynthetically usable radiation on the graph. PUR in this example is 87%.




Third,
After taking a closer look at PAR, PUR% as it relates to PAR...Here's the next evolution of this thread. Back to part of my opening statement above "The amount of white light we use is all about personal preference right, or is it..."

What happens with the white light (yellow & red) outside of the blue & green spectrum? It can improve viewing our tanks, some folks like a more white "daylight" appearance to our tanks. In my experience it can also contribute to some things I have strived to keep out of my tanks, hair algae. I'm not saying hair algae only grows in white (yellow & red) light but in my experience it greatly increases hair algae growth.

Here's a couple of pictures from the tank from the first reading (graph above with white light). Notice the hair algae, this tank rarely gets fed.



Now a picture of the absence of hair algae in a tank from the second picture (all blue light, no whites). This tank is 2 years old and gets fed heavily.


I know lighting alone does not define harangue issues (excessive nutrients) but I'm curious to hear other thoughts on lighting and any hair algae lighting observations.

Again @aestheticlibra, thanks for starting this thread, great topic!

 

[Steve Burton]

" it can also contribute to some things I have strived to keep out of my tanks, hair algae. I'm not saying hair algae only grows in white (yellow & red) light but in my experience it greatly increases hair algae growth."
I definitely agree with this, my experience too. Other algae also, I must clean my glass proportionally more as white light is increased.

 

[ActiveAngel]

Cool beans @dball711 . I guess that we are saying the same things then, and just using a different language/terminology. I wasn’t trying to put you down or anything. When you said “usable PAR was 1013”, I thought you had understood that usable PAR and PUR are synonymous. This really is a minor disagreement... however, it is leading to some false information.

-

To focus on what we do agree on; white light will increase the growth of hair algae more than blue light. This is absolutely true. But the reasons behind it are incorrect.

It’s not caused because the % went down. However, the cause for this decrease in percentage is the same cause with the growth of algae, so one can observe what appears to be a cause and effect relationship. Likewise, it’s also not caused because PUR went down. On the contrary, higher PUR would promote the growth of algae. The difference lays in the red wavelengths.

The symbiotic algae that lives within corals has evolved differently from many other algae in that it primarily uses blue wavelengths. Meanwhile, other algae still use blue light, but also will use red wavelengths. So by reducing the amount of red light (I.e., as a component of white light), you reduce the promotion of hair algae, and simultaneously increasing the percentage on your meter. But this is separate from PUR, which can be increased or decreased, and create increasing or decreasing promotion of algae respectively.

 

[Adam]

What I'm getting from this is the white channel increases PUR at a much lower rate compared to the blue channel(s) 400-460ish nm range. The more the white is turned up the higher the PAR level goes but the percentage of PUR, measured against the light from all spectrum's produced from the fixture(s), goes down. Even though the actual PUR level went up, marginally.

For me when I look at my tanks I like to have a little white. Most fish look like crap under all blues. Conversely, when I'm not looking at the tank I don't care what it looks like as long as the corals are happy. This would also be the case if you don't have many fish, like the way they look under blues or don't really care what your fish look like.