I thought I posted this build already, in fact I remember talking with another Mike (CoralReefer) about it... can't find it maybe it was on the old board and never migrated over, so I'll keep it swift and short (ha! who am I kidding, this is going to be an essay ). Long story short, built this LED array. The colors I wanted, the channel separation that I wanted, nothing out there did. I don't believe in red LEDs, green, cyan, or any of that other "full spectrum" stuff everyone clamors about. I want my whites white, and blues blue to pop the pop out of the coral pop! Ok I also wanted some "actinic" too. So decided on a 4 channel LED, with 4 clusters on the heat sink. The idea is I have my bright central light, with "bars" of LEDs on each side. Similar to having a metal halide with actinic fluorescent tubes. Channel 1: Is neutral white, use this because it has a good amount of light in that warmer (redder) part of the spectrum not as harsh as cool white leds. Channel 2: Is the color pop channel, all royal blue Channel 3: Is the other blue version, 475nm I think... I forget, it's a little less blue than royal blue, I also put in 1 royal blue too for every 2 blue Channel 4: is the "actinic" I believe these are 420nm violet LEDs, these are strictly for that dusk/dawn "I want to see a dark tank with mostly fluorescence" look. The whites and royal blues are Cree XT-E, the blues are XP-G (or XR-E.. I get those naming conventions mixed up), and I'm not sure what brand the violets are. But they all are solderless, meaning the only leaning over this I was doing was to screw them buggers in and attaching wires by pushing them in the holes. The layout Drilled heatsink. A drill press is your friend for this step. And make a jig All the buggers screwed on with thermal goop under them And wired up. Went with Meanwell LDD drivers, this turned out to be the cheapest way to get dimming. I used a Typhon controller (Arduino based). With a meanwell power supply rated at I think 320 watts, the LEDs only consumer 140watts at full power, but I planned on building a second fixture down the road. Do note, you do NOT want to keep the power supply inside the humid fish area, it will pull in humid air with it's fan and corrode the crap out of the insides (I found out the hard way) Everything on, it was a very fast picture which is why it doesn't look terribly bright. And here's the tank set up back in March. Note this was a rather quick emergency move to try to save corals which were dying in my other tank (either chemically, photosynthetically, or through a fish picking at them). This tank was only setup to be a frag tank temporally.. 7 months ago (ok it's still temporary I just didn't say how long ) Fast forward to a few days ago Things I notice is that the LEDs do a great job at growing algae. With no herbivores in the tank other than a lone turban/turbo snail, it's basically only kept in check by me. I was surprised at how well it could grow in a tank that does not get fed at all, yeah not even the corals. Algae grows really well in the corners, but I think that's an issue with tank geometry and flow. I borrowed the clubs PAR meter to take some readings of the light. On the bottom I get about 100, and this is with no lenses on the fixture. I didn't go with lenses for a variety of reasons. However out of curiosity I decided to see how much lenses would change the output. So I took the fixture down placed it on the ground and did like Sanjay with his lighting tests... except quite a few less data points. Due to the location of my testing, I only had one LED driver handy (didn't want to take down my power supply) so these values are only with the white channel, which is a total of 12 of the 48 LEDs. Distance was 24" away, in air, so I expect lower values in the water, but then again this is only a fraction of the LEDs. I had two types of lenses that I tried, some "cheapy" ones I got through eBay, and the ones RapidLED sells, both are at 60° labeled Lens 1 and Lens 2 respectively The first test was starting in the dead center of the fixture and moving outward in the long direction. I stopped about 3 inches beyond the end of the fixture. As expected the LEDs without lenses had a fairly constant output, dropping only slightly as you went out. Comparing this to the numbers in the tank of about 100 on the bottom (but with all the LEDs) I can get a feel for what percentage the white LEDs make of the total light output (somewhere between 1/4 and 1/3). While I expected the lens versions to be stronger, it really shows how much stronger, over 7 times the output, however it does drop off quit a bit. As you go further out, mind you still more powerful than the version without lenses by a long shot. This next version moves away from the LEDs in the short direction of the fixture, I didn't start in the dead center of the fixture, started at one end and moved back, I was more interested in how fast the light drops than the actual light output (after all I wasn't firing all the LEDs as it was). Starting in the center of one end I took measurements at 3" increments, the main difference here is moving over a bit won't put the sensor over a new cluster of LEDs, so I expect this similar types of numbers dropping off if I took measurements beyond about 3" in the long direction above. Again without lenses the spread was more, and it's interesting to see after about 8inches from the middle of the fixture you get more power from the LEDs without lenses. In fact I went all the way down to 2 on the PAR meter with lenses at the last data point and wanted to see how far I could go without lenses to get that value, and while it seems quite nice that I can get almost 4 feet away from the fixture... 2 par ain't diddly squat so if anything it's more a testament to how much light won't be doing anything useful. Conclusions: It's no surprise that with lenses you get a much greater light output than without lenses, the trade off is that you get that power over a much smaller area. The upside is with lenses looking at the last graph is that you'll be illuminating the outside of your tank or your glass a lot less if you use lenses For kicks and giggles I measured the royal blue channel and noticed power outputs almost 100 more than the white for the same number of LEDs, doing some quick back of a napkin calculations I figure I'd get around 1000 PAR with all the lights on w/ lenses @ 24", which is roughly half the brightness of the Sun. To further add to this, I checked against Sanjay Joshi's articles on LED fixtures to compare numbers and unless I'm reading his numbers wrong (which I'd like to think I'm not) it seems my fixture with only whites is about as strong or stronger than other commercial fixtures like the EcoTech Radion (pro version), and with all might lights on it absolutely destroys any commercial fixture of similar power output. Which is kind of cool and makes me feel like my time and effort was well spent in designing this. For kicks and giggles I put lenses on one white/royal blue cluster to see how the output changes in the water, and it seems like it increase by a factor of about 3.5 or so, I imagine that would almost double if I put lenses over all the LEDs.