I ran Halides for around 25+ years (1986-2013). Decided to start working with LEDS when I started planning for converting my old 180 to the current 300.
Decide whether you want "glitter lines" or not. If so, you're going to want a point-source such as a Kessil or somesuch. If a more "T-5-ish" ambient light is your preference, there are many choices out there that can provide that and a heck of a lot of PAR as well. Most of them look great, are incredibly controllable, and produce super results for the livestock. Ask folks who are using the fixture you're planning to use about their experience with them.
Use a high quality PAR meter that is calibrated for the blue end of the spectrum (something like the Apogee MQ-510) to set up the LEDS and aim for the lower end of the desired scale initially - say somewhere around 150-200 PAR. Ramp up to your desired PAR level gradually. I brought it up about 5-10% a week.
Check that your spectrum covers the animals' needs. Heavy blue is fine I guess, but I prefer a more "shallow-water daylight" spectrum with high natural color rendition. The blue is still there, but the reds and greens are, too.
I think my reef does pretty well on LEDs. Sorry the video is about three months old (I didn't realize the Gold Flake grew so much so fast...yeesh). I guess I need to post a newer one sometime. PAR peaks at around 500 during midday at the top of the reef and about 350-400 at the rubble line. I can push more, but I begin to really inhibit growth at that point and bleach coral.
Cheers,
Ray
