Thanks for putting up that link. I had never heard of that EcoTech report. I found it interesting. I didn't learn much, but it did confirm pretty much everything I've been telling people here for some time now and I appreciate reading that somebody doing a scientific study (although with a serious commercial point of view - that leds are better than t5 and MH). That was the part I kind of took exception to. Their photos showing growth and health being so much better under leds vs MH or t5 to be a bit out of line with the composite anecdotal results of reefers here at RC.
I'm a huge user of leds, and I believe that leds can grow corals (any corals) just as fast and healthy as MH or t5. But at the same time I think at least half the people here at RC would say that MH or t5 are better, which flies in the face of what this paper tries to show. And I don't think those people who believe in MH and t5 are wrong. I don't think leds produce a light that is significantly better than a MH or t5 fixture. I think they all grow coral and one is not significantly better than either of the other two. That is the commercial/marketing slant to this paper, which they present as being scientific and accurate, which I find somewhat distasteful.
That said, I think led fixtures have some serious advantages to MH or t5 in terms of user features that make them more popular currently than MH or t5.
Lower heat production
virtually no bulb replacement costs
somewhat lower energy expense
intensity control
sunrise/sunset/moonlight control
color control (without changing bulbs)
ability to run different modes with the push of a button (sunny, cloudy, all blue, moonlight, custom anything and on and on)
And I willingly admit that none of these advantages has much, if anything, to do with growing healthy coral. But they are advantages I appreciate as a user over my tanks.
And the paper never addressed the 2 issues with leds I find as important.
1) Disco effect and shadow edges of red & green. And as a point source light (pucks) and being 24" off the water in this experiment, the Radion has far less of this issue than led fixtures with arrays of light like many/most other led fixtures. However, eliminating the red & green leds does negate 95% of the disco effect. And they really aren't necessary IMHO. For 5+ years I had leds with no red or green leds (I covered them with black electrical tape) and all my corals grew and colored up as well as they did when I was using MH & t5 hybrid fixtures.
2) The directional focus of led light. For the most part it is more straight down when compared to MH or t5 which use reflectors which bounce light in an almost infinite number of directions. This causes 2 issues for leds, deeper shadows under ledges or overhangs and poor growth/health under some bigger coral colonies (mostly sps stick corals). The directional flow of light from leds has a much harder time getting under growing colonies and they tend to die back under an ever increasing upper layer of growth. I've experienced this issue myself, so as far as I'm concerned, there is no denying it. It wasn't discussed in the Eco Tech paper, but in their defense, they were growing frags, not big colonies and their fixtures were 24" off the water which is something almost none of us would do.
