90gal 48X24X18 LED arrays?

[CalmSeasQuest]

I'm sure Evil will chime in with better data, but I don't agree with those estimates. I'm running 2 AI units (48 3W Crees using 40 degree optics over a 24X20X20 tank) and it's MUCH more light than needed. I almost killed everything (all SPS) in the top 3rd of my tank and sent my RBTA into hiding until I figured out that you can't judge LED PAR output based on looks - It's MUCH MORE than any comparable "looking" MH or T5 setup. If you do, you will bleach everything.

I've got mine hung about 12" above the tank - no shadows, nice even light dispersal but even after 2 months, I'm still acclimating. Thankfully, the new AI firmware allows for the creation of ramps that allows you to create a more natural, acclimation process. Mine currently looks like this...

Blue 06:30/89/100% 11:00/119/100% 14:00/239/100% 22:00/59/4%
White 07:00/239/50% 11:00/119/95% 14:00/239/20% 18:00/239/0%

(i.e. - start time/ramp duration in minutes/final power output)

You can see that my tank only receives close to the maximum light output for a couple hours a day - even with this, I've had to relocate some SPS lower in the tank.

This allows for customized gradual sunrise/sunsets and midday PAR increases without blasting everything with 984 PAR for 12 hours a day (actual measurements from a single unit at 12"). It also creates a perfect blend between PAR and color balance. At the higher white outputs, the tank is more yellow/less blue than many would probably prefer (I'd guesstimate it around 10K-12K at 100% white.) By using ramping, you can have the tank "Windex" blue in appearance in the mornings and evenings when it's most likely being viewed (if you prefer) and still have the maximum PAR outputs during midday - Just the way occurs naturally.

A single AI unit (or a comparable DIY) cranks out 2000+ PAR at 4". IMHO and based on my experience with the AIs - Assuming the same LEDS and optics, anything over 96 LEDS would be a waste on a 4' tank. They would probably result in photoinhibition problems in the very top of the tank unless the lights were hung very high or used for brief photo periods.