First things first, you need to get the lights mounted correctly for optimum height and spread. I have a tank of similar dimensions, so I'll tell you what I found both in my research and in my practical experience running 2 Primes and 3 Primes over the tank.
Height and Spacing:
I found that the
BRS recommended settings for the 40 Breeder worked great for me for height and spacing. For 2 Primes, the lights should be centered 10" in from each end. For 3 lights, the outside ones should centered 8" in from each end (and the center light centered, of course). Mounting height should be 10" off the water in either setup.
Schedule and Intensity:
You can really run whatever schedule you like the look of (Pennywise, Saxby, etc). Honestly, they'll all grow coral as long as the intensity (PAR) is set correctly. Pick something that runs for about 12 hours, and for SPS, I'd recommend something that has a decent amount of green/red/white in it, for at least part of the day.
Get your hands on a PAR meter. You can make educated guesses and probably get close, but there is no substitute for spending 20 minutes with a PAR meter and getting things setup correctly out of the gate. Check your LFS or local Facebook groups to see if you can borrow or rent a meter.
I will add this... In the myAI app, when I ran 3 Primes on my tank, I ran the outside pair on one "tank" in the app, but I ran the center light independently. I ran the same exact schedule on all the lights, but that allowed me to adjust the center light lower to compensate for light overlap hotspots in the middle of the tank. I found that I ran the middle light at a MUCH lower intensity than the outside lights to get an even blanket of light over the entire tank.
Misc. Thoughts:
I ran shades and diffusers for a while, but after a lot of testing with a PAR meter, I ditched them all.
First, if you have the lights mounted at the proper height, light spill out of the tank will be minimal. The shades cut down so much "glare" that they actually limit the spread of the lights. Kind of defeats the purpose.
Second: If you have the lights mounted properly, blending is actually pretty good. The diffuser lenses cut down shimmer and potential disco ball effect, but they also CRUSH your PAR output. If you have plenty of power to spare, it's not a big deal. But I'll tell you that if you're aiming for SPS in a tank that size, you won't have a ton of PAR to spare.
Also... Watch this video. Watch it all the way through, 2 or 3 times. You will have a MUCH better understanding of how your lights work and what things (height, spacing, etc) can change or effect other things (spread, output, etc). It really is the best source of info for the AI Prime available anywhere.
