DIY LED for Nano SPS Tank

[Biglurr54]

I am building a 6 gallon tank at my desk. (approximately 24x8x8) Its will be tied into my main system for stability. I need some help with working out the lights for the tank. I will be doing a DIY LED fixture due to the odd size. 24 long but 8 wide and 8 deep. I was thinking of doing 4x warm white, 5x Luxeon Cool Blue, 5x Luxeon Royal Blue, and 5x Hyper violets. This would be on an 18" heat sink. I would like to have the light mounted at the ceiling and spot light the tank. This would be about 48" from the ceiling to the bottom of the tank. What degree optics would I need to spot light the tank and keep light spill minimized?

Also is that an appropriate array of LEDS for for coloration of SPS?

 

[oreo54]

Start w/ arranging the diodes in a 2x18 center to center pattern.
So really 2 rows 10 columns.
Ideally you would use 36 diodes to keep the density equal in both directions..
Bothersome that you have 1 per inch in one dimension but 1 per 1.8" in the other.. but not horrible.
I evened it out a bit .. 10 of each color.. so 40 total
2 rows of 10.

you want to cover 24x 8 at approx the water line
So assume about 40"

So you have 3" extension needed on the 18" side.
9-ish degrees...

LED Lighting Beam Angle Calculator

A simple calculator that determines spot size by a light's beam angle

store.marinebeam.com

Only diodes you need to be concerned with is the edge ones.. rest will fall into place
@ 40" and 9 degrees spot diameter is 6.3"

3.15 + 18 + 3.15 = 24.3
3.15 + 2 + 3.15 = 8.3

JUST a START (and admitting that it is not "exactly correct, more of a ballpark start.).
A bit pricy but listed as glass (good thing)
They have 5 degree AFAICT and others but I'm not going to dig for the 10 ones..

 

[Steven Garland]

If it were me,I would do 4 clusters 6" apart consisting of ww,mint,4 royal blues,1 cyan,1 cool blue and 2 violets 390-400 and 430.

Even coverage,no hot spots and even light and par.