[Mxx]

I can't comment upon the PAR, but after experimenting with a mixture of cool and warm white LED's, I'd definitely opt for the neutral white.

I don't understand though why lifting LED's a little higher would decrease their intensity. They are very directional of lights, so are far from being a point source to which an inverse square falloff would be applicable. Besides, with that driver you could just dim them slightly to get them to last longer and run more efficiently instead.

 

[Mxx]

What was it about the WW/CW combo that made you prefer the NW lights?

Neutral white would have more accurate and natural colour rendition more similar to daylight, while cool white and warm white can each be a bit too blue and yellow respectively even in combination, in my own opinion. The cool white in particular really seem to wash the colours of fish out, although that is what many people nevertheless seem to use, which seems odd to me unless you're running a reef tank.

If you look at the spectral outputs of the those three LED colours, they all seem to lack much light in approximately the turquoise part of the spectrum. So when I do another tank I may even look at supplementing those wavelengths with a few low power coloured LEDs. I'm by no means an expert on LEDs however.

 

[Mxx]

CREE don't seem to have them, but you can resort to other suppliers and can of course cheaply procure some coloured LED strips on Ebay. It's not as if you require a great deal of intensity to fill in just that one part of the spectrum. Green LEDs are around 525 nm, and Aqua LEDs are about 505 nm, so with a combination of those two you could potentially fill out the lighting to better mimic the spectrum of sunlight. Your plants don't really require that, but I would personally expect it to overall make your tank and your fish look better.

 

[Mxx]

Sounds like you have a good plan.

FWIW you can actually run 14 XPG's (in series) or 28 XPG (in parallel).

You can run 16 XML's in series or 28 XML in parallel.

This is on the Meanwell ELN60-48D. The XML's have a lower forward voltage meaning you can run more of them up to the 48v max.



And here is a quick glimpse of the spectral data we collected over the weekend of a bunch of LEDs. This is the cool white XML at 700, 1500, and 3000mA.

Sounds like a pretty wild weekend you had! ; ) What tool did you happen to use to collect this? And does it give any readings such as the actual total PAR and/or lumen at each current? Helpful though, thanks.

 

[Mxx]

What is the PAR of the NW vs the CW?

Seems the blue spike makes the difference as the WW have a lower blue spike and are lower PAR, but the NW & CW have about the same sized higher blue spike.

Since I've recently invested $95 in two individual T5HO fixtures with quality reflectors, I don't have any spare bux this month to pursue the LED's. However I know where to get 'em when the time is right. Meanwhile I'll head over to the scrap/surplus metal dealer and procure some decent extruded Al stock suitable for the heatsinks.

I'm planning on a single row of 15 CREE XM-L 2.25" on center. No optics so I hope there is good overlap. I'm not sure how well they will cover the 12" wide tank floor. Hopefully the glass refraction will reflect most of the dim wide angle beam back in and offset any dimming of the beam at the front and back tank substrate. I'll just add a second string later if needed.

Judging from the graphs, and as PAR emphasizes wavelengths both in the red and blue areas, the WW may even have the highest PAR being that the blue spikes of each are relatively narrow and considering that the WW have a great deal of area under the line at the red end of the graph. Similarly, the NW should have higher PAR than the CW as their blue spikes are equal but considering that they have red as well. However, I'd personally be more inclined to pick light on the basis of what looks good rather than simply PAR.

In my opinion the light bouncing off the front pane should help illuminate your fish. I personally prefer to see the colors and iridescence of my fish, rather than seeing a backlit X-ray look to them. So I wonder if you'll eventually end up adding another string so that you can have one of them closer to the front for primarily that reason even.