So I have started on my third revision of LED lighting for Algae Turf Scrubbers.

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First, why go LED ... again?

Long term cost is probably the biggest reason.
Switching a standard SM-100 to LED could save $150 per year in bulbs + electricity.
And since I need roughly 4X, that is $600 per year. A really big number!
Plus:
Normal CFL/T5 needs to be changed every 3-4 months. I always forget.
LEDs use nice safe 40 Volts around all that salt water.
No mercury waste.
Much less heat transfer to the water.

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Other key threads:

1) Very detailed analysis on LEDs here:
viewtopic.php?f=3&t=435
The middle section has a ton of good detail on spectrum and so on.
I do not plan to repeat that in this thread.

2) The big turf scrubber this light is being built for:
viewtopic.php?f=3&t=645
Just as reference.

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What are my three revisions:

# Rev 1 = Test simple CFL replacement.
This was really just a quick experiment to see if LED works. It did.
BUILD:
- 3 x Warm white
- 2 x Red.
- All 3W LEDs, but running at 700mA, so 12W total.

# Rev 2 = Spectrum optimized.
This was meant as a real engineering analyisis.
How to create the perfect LED system. It was done with a lot of
input on one of the big threads here.
Well, it worked well of course, but honestly, really not that much better
than the simple one with warm whites. Just a bit less waster power.
BUILD:
- 8 x Special Deep Red.
- 4 x Blue
- 3 x Warm white.
- All 3W LEDs, but running at 700mA, so 35W total.

# New Rev 3 = A lot bigger
This is meant for a log bigger tank. 250 Gallons.
BUILD PLAN:
- 20 x Cheap Warm White
- 16 x Cheap Red
- 8 x Special Deep Red
- 4 x Blue
- All 3W LEDs, but running at 700mA, so 110W total.

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What have I learned over the various revisions:

# LED Intensity / Wattage:
LEDs are pretty powerful. My REV-2 can easily burn the algae if
I run them too long / day. I am down to less than 12 hours/day on that one.
I don't really have a ton of data of course, but from my experience,
and looking at others on line:
* Moderate filtering = 0.25 actual LED watts
* Strong filtering = 0.5 actual LED watts
So basically 2X the efficiency of a good T5 system.
And thus probably 4X the efficiency of a standard CFL bulb system.

# LED Spectrum:
Clearly, LEDs like the Blue end and Red end of the spectrum.
Deep Red (Not standard red), and blue seem to really hit it well.
But unfortunately, simple colored LEDs have a tight spectrum,
so it also really helps to have some warm whites to hit missed areas.
Ideal seems to be N * (2 Deep Red + 1 Blue + 1 Warm white)
FYI : Warm white is really blue + a wide spectrum in the red/yellow/orange.
All that said, it does not really seem to matter all that much.
People have had complete success with all warm-white, basic red+blue,
and various other mixes.
So while the Ideal may be great, it is probably not worth the extra cost.

# Cheap Ebay LEDs from China change the game.
You can get warm whites and reds from Ebay at less than $2 each.
And these are decent 150lm LEDs.
If they fail, cheap enough to buy spares.
But they do not have the deep reds or other fancy ones.

# LED types:
The sweet spot seems to be 3W LEDs, run at 700 mA, so 2.3 W.
These have really high efficiency and longevity.
Running them below rating helps that even more.
Going larger than 3W leads to thermal and light distribution problems.
Too much liht and heat in a single small spot.
LEDs smaller than 3W are a lot lower efficiency, higher cost / luminance,
and mean a ton of assembly and soldering.

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So why my exact choices?

First, the obvious:
- 8 x Special Deep Red
- 4 x Blue
I already have these, and I know they work well, so I am simply moving them
from my Rev-2 to Rev-3.

Now for the others:
- 20 x Cheap Warm White
- 16 x Cheap Red
I know from Rev-1 that warm white + red work well.
And I also have a bit of the blue and deep red already covered.
But most importantly, these were really cheap on ebay.
Those 20 warm whites were only $50, which included shipping.
And supposefly 150 Lumens, so pretty decent quality.
(Of course, ebay from china ... hard to say)
But I have looked at them, and they do work, and look fairly bright.

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Lots of details to follow.
Yes, drawings, pics, and eventually results. I promise.
But probably rather slowly.
Big new tank, and SO many things to do.