We're limited by what the LED manufacturers produce. But that doesn't mean that the available wavelengths align sufficiently with what the organisms we're trying to support want and need. We do know that T5 and MH work really well supporting reefs. IMO, I believe we need to work toward making our LED builds replicate the conditions created by lighting that we KNOW works. Keep my PAR example in mind.
Thanks very much for bringing some data to the party. When this "issue" first came up about a year ago, I tried to contact some of the more biologically-minded resources we have in the reef community, to get some answers about what spectral qualities we needed for "good" performance (growth, looks) in a reef tank, and whether or not the obvious differences in spectra from LEDs and other forms of reef lighting mattered.
It was basically a dead end. I got frustrated at the lack of solid information. Then, I had an epiphany - in the absence of a clear direction from the scientific field, we are essentially doing the experiments ourselves.
First, we need to define our criteria. What are we after? Matching natural lighting? Best growth? Best color? How do other tank conditions impact these criteria?
In the end, I'd be willing to bet that most hobbyists are after some magical combination of growth and color. Looking at results of LED builds so far, we have absolutely got the growth thing nailed. People are able to grow every kind of coral imaginable under the right intensity of LED light, with the "common" RB/CW blends.
That leaves color. For better or worse,
color is subjective in our hobby. If a coral is pink in one tank, and it turns orange in the other tank, there is no black and white answer about which state is better - some might not be bothered, some might like the orange state, others might like the pink state.
Take that out a step. If a coral is pink under MH, and it turns orange under LEDs, does that mean the LED tank is "wrong" or "bad?" Again, a question we cannot answer, since it's clearly a matter of preference. In some cases there may be some obvious cut and dry examples, i.e. corals that are nice under T5 but all turn brown under LEDs. But, I don't think the typical LED rig has any inclination to create that sort of situation. Yes, there are some reports of some corals in some tanks turning "less pretty" under some LEDs, but the
same exact thing happens when some people switch from MH to T5, for instance. So, again, I don't think we can clearly say that there is a "better" way to do things at this point, from a spectral perspective. Surely, LED spectra are different than MH and T5 spectra, but since MH, T5, and LED can all make corals ugly or pretty, I don't think it makes sense to blindly try to copy the spectra of a given other technology when implementing LEDs.
Which is why I continue to suggest the "typical" CW/RB blend when people ask the question "what LEDs should I use?" Sure, this combo has produced undesirable results for some people. But it has also produced great results for many other people. And unfortunately there isn't (and probably never will be in the near future) a clear answer from the scientific community that "X spectrum produces the best colors in corals" AND there haven't been enough "alternative" LED rigs built to give a clear indication that any other combination is obviously better. It's great that people are starting to experiment with other color combos, but when someone totally new to the concept with no understanding of the variables involved says "what LEDs do I need?" IMHO given the current state, we are best off suggesting CW/RB, because we know it isn't outrageously bad. Once there have been several dozen "alternative" builds running for a year or more with coral progress photos, maybe then we can start altering this standard mix. In the end, I'm sure we'll end up with a variety of people using a wide range of diffferent mixes, in the same way that different people like different MH lamps or T5 combinations. If I want a 20kk XM on my tank, and you want a 15kk Iwasaki on your tank, that doesn't mean that you're wrong and I'm right, any more or less than CW/RB vs. NW/RB is wrong or right.
