Of course I agree with you that we should avoid blanket statements. Problem in any aquarium forum is that people will state what they notice and choose the results they like showing pictures and videos. Therefore such division of preferences and some times harsh arguments. At the same time we know that the majority posting their opinions here will never have access to any scientific device to measure any of the previous data suggested. We depend on people like you to try understand more.
I agree also that we should examine in details as to why such results are happening. But how? Who could do that? And what are exactly the facts for the results we see and what to look for as for real factors?
Another problem we often face here is that "good results" have many meanings to so many different people. It is so hard to determinate a based pattern in order to drive such comparisons besides approaching the natural original aspects of the coral colonies in question. That is MHO. Specially because of the large diversity of qualities the same coral species will show under so many different "diluted environments" offered by people in the hobby.
I think an experiment should have different fresh daughter wild colonies from the same mother colony to be exposed to the different types of light to start with with proper acclimation to the individual light sources in the very same system (water parameters/system maintenance).
It is important to note that results are different and personal preferences will determinate what people like here in this forum. So what one thinks is "best" will not necessarily will be to another. And after all that we still have the differences among the types of light.
Besides all the previous aspects of light on the table, including PAR, PUR and intensity measurements, and all the variations of them, specially pointing the long term aspects of exposure (differences in photoperiod, as an example), what would be the points you would think we should consider to determinate the different results of light on corals namely: "colors and growth rate" normally published by many?
I think the real spectrum of each source (well represented often by limited charts) is what makes the differences. The photons produced/emitted by halides are different than the ones by LEDs in terms of limitation. Due to the broadband spectrum properties of halide bulbs independent of labelled Kelvin numbers on the halide's boxes, I think the photons produced by halides are better at resembling the natural photons produced by the sun. That is, the photons halides can produce embrace and offers a better quality to the living organisms. As we know the photons by LEDs are different in nature basically because of the way they are produced. Halides and T5s photons are produced by gases. The LEDs are different, produced by 2 electrodes. Effects and results will have to be different on living organisms. Another major difference is CRI (Color Rendering Index). LEDs have 65-95 and halides have probably the best source of high CRI white light in the market. If we talk about Foot Candles we normally see the advantage of LEDs in numbers, but we know the use of good quality fixtures will distribute the light from halides and therefore make up for the know losses in comparison associated with omnidirectional light output transfoming the environment and providing a blanket favoring as a whole. There are so many aspects...
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I do trust graphics to some extent, but also see them more as a reference, many times commercially speaking when by companies, to what really happen. That is why is so hard to trust and lay on them 100% IMHO. They are very good references in their majority, I would say.
Another fact to spectrum is blending and direction emitted in terms of LED. Again UV and IR are also what I think makes a huge difference using halides. I would like you to leave here your detailed comments on that part as well. I've been waiting for that long time, please.
To be specific we can talk about a coral that you and I know: Porites lobata. If we see some of the strains in the ocean, they are so bright yellow in shallow water that is like a magnet to our eyes. Truly beautiful. Such coral can maintain those natural pigments (and natural colony shape) under metal halide bulbs but not so much under LEDs alone. I believe that was also the case with Dr. Sanjay Joshi with his yellow Porites sp. How can we stipulate, in that specific case, what determinate maintaining the color of the coral (or similar Porites spp. in the same terms)? When he had halides over his tank the coral was bright yellow and after he changed to LEDs it became dull gray. I know this is an isolated case, but we need to bring something here as a comparison and unfortunately there is no way to really find out because we are not sure if he did any other changes in the system that would affect, even if he claims not to change anything. I just want to know your thoughts on possible ways in regards to light alone, if you can.
I really wish you could go deep in your thoughts here and try to expose possibilities and question marks to bring some of the light properties in order to explain what we read so many times when people report their changes from LEDs to halides like in this thread. That way most of us would be able to have in mind all the aspects of results and try to understand more about the results and the facts posted.
Maybe we will need an article after your explanations here.
I appreciate your help very much!!