Bay Area Reefers

I am gradually grinding through the tasks for my new 250 gallon tank.
Next step : Lighting, so time for an LED thread.
Note: This thread is not meant as a basic how-to on LEDs.
I have experience on that, and will happily help others as needed, but there are a
lot of other good basic threads, here and in RC.
This thread is about taking LEDs to the next level. And maybe failing - who knows.

I want to start with a short story:
I built a small 2 x XPG cool White + 1 x XPE Blue + 1 x XPE Royal Blue LED cluster on a heat sink.
I pushed my current tank lights over a bit, and looked at it.
Results were GREAT!
A few minutes later, I realized my mistake.
So I turned OFF my other tank lights, and tried it again.
Bummer - did not look nearly as good. A bit washed out. Pretty good, but far from great.
So the combo was great, but alone, not so much.

SO THE PREMISE : CURRENT LED SYSTEMS ARE ONLY "PRETTY GOOD"
As I have personally experienced, and as I see on the net,
the current standard build of Cool White + Royal Blue is really not bad at all,
but very few approach my ideal of a high quality Metal Halide + T5 Actinics.
I am hoping that can be fixed.

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# THE PROBLEM WITH COOL WHITE + ROYAL BLUE:
This is the most common setup these days.
And like mentioned above, the results are actually "Pretty Good".
Plus you can pretty easily tweak the amount of blue to get the color temp you want.
The thing is : It looks nice given a fairly uniform white target.
So on bare live rock, can look great.
The problem is : It is your eye fooling you. The spectrum is actually pretty bad.
You have HUGE peak of blue at 450 nm.
You have a bump of light from roughly 525 nm to 625 nm, green through orange.
But you have almost zero reds, especially deep red.
Plus, you miss Cyan, and the deeper violets.
So while you can trick the eye into thinking it is white, it is actually far from it spectrally.
The problem is if you have a red coral for example, and no red light, it will look almost black.
Now there is red, just not that much, plus there is fluorescence, so you will see some reds.
But in general, it will look washed out and greenish-blue.
Also, chlorophyll need that missing red.

# THE PROBLEM WITH EVEN SPACING:
Again, this is the most common setup these days.
A lot of systems, even professional, evenly space the LEDs, often alternating White / Blue.
That is wrong. You really want to keep LEDs of different colors very tightly clustered.
If you don't, you can get terrible color banding effects, especially in shadows or with a rough water surface.
What happens is that you will have some regions where blue dominates, and some where white dominates.
For example, directly under a blue, next to a high rock that blocks the nearby white.
By itself, normally the color is really not that different, since light bounces around a lot.
But your eye is really good at detecting subtle differences in a pattern.
As a result, you get a mottled effect, and really notice the odd bluish areas or odd yellowish areas.
Note that optics make clustering hard, and make the problem worse.

# THE PROBLEM WITH NEUTRAL/WARM WHITE:
So a common "fix" you hear about is to add a few neutral and warm whites.
This is done usually after looking at the data sheet, and seeing how it looks shifted a bit toward the red.
The thing is, the data sheet curve is deceptive. Oddly, the best thing to do is to look through a cheap spectroscope.
What really happens on NW/WW is that the orange and yellow end is raised considerably, and the blue is dropped.
Yes, there is a bit more red, but not enough to fix the root of the problem.
So you move the energy just to where you don't want it - yellow.
Then you add a lot more blue, so you end up with largely blue + yellow, which is even more washed out looking.
To make it worse, people add a few NW/WW here and there, and they end up widely separated,
which in turn cause color banding problems.

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### BACK TO THE BASICS ####

The big problem in my mind is having multiple issues and targets as follows:

1) Match coral spectrum. (PAR)
Clearly, chlorophyll need blue and some red. But it is more complex
since there are many more cartinoids, and coral seems to be adapted more toward the blue.
Best seems to be : Lots of blue, a bit extra red, and moderately low flat values in between.

2) Match the human eye. (Lumen / CRI)
It needs to look good of course. But again, it is not that simple, since the
eye is more sensitive to certain wavelengths. And to make it worse, it does not match PAR.
Best is a fairly flat spectrum, perhaps with a bit more blue for color temp personal taste.

3) Reduce power.
A big point of going with LEDs is to reduce power.
But that means more than just replacing it. You need to pick efficient LEDs, and
you need to not waste a ton of power in unnecessary wavelengths.

4) Reduce the yellow look.
Fish tank water tends to get a yellow tint. Dead algae, and other bio.
Plus, most of the pleasing colors you want to "pop" are red + blue + green.
As such, you want to reduce the yellow/orange part of the spectrum.

5) Fluorescence.
A lot of what we talk about when making colors "pop", is actually fluorescence.
Hence actinics.
It is key to note the science here. : A shorter wavelength is emitted as a lower energy longer wavelength.
Because of that, we generally want as short/high energy as possible. Royal blue works, but UV works better.

6) Reasonable cost/build.
We are limited by the manufacturer and what we can buy.
Plus we are limited by space, drivers, soldering, and more.
A perfect system may not be that practical.

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# BACKGROUND:
My current tank is a mixture of LED/T5, and my turf scrubbers are 100% LED, all DIY.
Plus I have done a few DIY LED lights around the home. So I have a fair bit of experience.
But I have never done a 100% LED main tank before.
New Tank is about 250 Gallons. 88"L x 30"W x 24"D.
I plan mostly softies / LPS, but center raised section will be SPS.

# MY PLAN ???
Still working on that.
I have a lot of LEDs to play with.
I have a Lux meter, and a cheap spectroscope.
Lots of soldering and tinkering to do. This is where the thread comes in.
Any and all advice is very welcome!!

The current theory:
Have a cluster that is partly the normal Cool White + Royal blue.
But also add a set of smaller 5 mm LEDs, that "tweak" the spectrum, particularly
in the deep red and deep violet.
The cluster will be mounted with LEDs clumped as tight as possible, on a single large heat sink

# LED CLUSTER
- 1 x XP-G Cool White @ 1200 mA
- 1 x XP-E Blue @ 700 mA
- 1 x XP-E Royal Blue @ 700 mA
- 1 x 5 mm Deep Red 660nm @ 25 mA
- 1 x 5 mm Red 630nm @ 25 mA
- 1 x 5 mm Cyan 505nm @ 25 mA
- 1 x 5 mm Violet 420nm @ 25 mA
- 1 x 5 mm Semi-UV 400nm @ 25 mA
CW = Cree XP-G, 6500K+, buy special bin toward cool
RB = Cree XP-E, Royal blue, roughly 460 nm
BL = Cree XP-E, Standard blue, roughly 475 nm
Probably need 40 of these cells.
CW/RB/Tweak will all be independently controllable, so I can play with the color a bit.
But not dimmable on the fly.