replacing 250W MH setup... LED options please

[grigsy]

Most economical solution (and the best one IMO) would be to simply replace the Lumatek ballast with a 250 watt M80 ballast. They run Radium 250 watt bulbs at higher PAR vs Electronic ballasts.

That would cost you about $150 or so and be great lighting for reef, especially SPS. If you were to change out the lighting, it would cost a lot more than just replacing the one ballast.

[dkeller_nc]

Originally Posted by yacn

I disagree.
Disco effect is created by the lenses....which can easily be changed out or ordered specifically to avoid this.
LED's are made by 3 or 4 companies....people over estimate the differences between them a lot. There are more and more LED color choices available now that weren't a few years ago. People also like to put price with quality. I think too many items are over priced in our hobby.
If you go and buy the over priced and expensive LED options out there it isn't worth it for larger tanks. But there are plenty of less expensive options like I suggested earlier that would work fine and save you $$$ on larger tanks.

Just for the sake of newbs that might be reading this:

The "disco effect" isn't fundamentally caused by the lenses in front of diodes. It's caused by the fact that diodes are essentially point light sources, and most (except for Kessil) LED fixtures use separate, discrete diodes of different colors. The refractive front caused by waves on the tank's water surface will generate a color separation because of these differently-colored, space-separated point sources. It will be less noticeable if the diodes aren't sharply focused (i.e., "lensless"), but its still there.

While it is true that all LEDs are manufactured by 3 or 4 companies, then put into fixtures by dozens of companies, there are fundamental restrictions on spectrum because of the physics of LEDs themselves. Specifically, all primary color LEDs generate light in a certain, narrow spectrum, and all spectrums within the visible, UV and IR ranges aren't readily available. Re-emission LEDs, such as cool white and warm white diodes, spread these narrow spectrums somewhat because they use the light emitted by the diode juction to excite phosphors, which re-emit the light on a broader spectrum than the stimulating radiation. Nevertheless, however, white and warm white diodes have a much, much more restricted spectrum than incandescent/fluorescent/metal halide sources.

Finally, while the situation is improving, inexpensive fixtures typically eschew the "ends" of the visible spectrum to keep costs down - this especially true in the near-UV spectral range. More expensive fixtures address this spectral range (410 nM and less) better than the inexpensive ones, but their radiometric output in this range is still quite poor compred to your average metal halide. This may, or may not be, the source of color-shifting and poor health of certain acropora species, which has been widely observed by the community, including experts like Sanjay Joshi.

In conclusion, and keep in mind this is coming from someone with a scientific background that's an LED user - it's incorrect to state that LED fixtures, even high-end ones, produce the same quality of light that is present in the traditional metal halide, metal-halide fluroescent and fluorescent set-ups that have been used in the past. And it's not just an issue of intensity calibration and getting enough fixtures to cover the tank's area and reduce shadowing.

It's unclear whether diode manufacturers and tank fixture manufacturers will be able to address these issues in the future, but many of us that are LED fans hope so.

[Nic33]

As someone who is installing led despite the limitations is there a list of corals that are known to not do well with them?

[ReefWreak]

Originally Posted by Nic33

As someone who is installing led despite the limitations is there a list of corals that are known to not do well with them?

There aren't any specific corals that don't do well that I have seen.

LEDs are very situational because of their point-source nature combined with their efficiency. MH is easy because it's point source, but huge inefficiency, even with a good reflector. LED are point source and efficient, so we're learning the downsides to that, things like less reflected light getting to the undersides of corals (acropora/SPS in particular).

It doesn't hurt their health as far as I've experienced, it just means more often corals start to recede at the bases or under the coral head. It might cause trouble once the colonies are huge and grown out, but even a year's growth on my corals and I'm not having problems.

Everything else seems fine.

A situational consideration to think about is the efficiency of the lights, how the LEDs can bleach corals much faster towards the top of the tank. I have a number of LPS that I have not moved off of the sand bed in my biocube, because they bleached if I raised them higher up in the tank too quickly. It was easier just to leave them in the lower part of the sand bed. I never really acclimated much with my old 250w radium metal halides in my 120g tank, even with good reflectors. You have to be more sensitive about acclimation and placement with LEDs because of the concentrated intensity of the LEDs, but no specific coral "doesn't do well" under LEDs.

[dkeller_nc]

Metal halides in fixtures, btw, aren't point sources - they're essentially the equivalent of a light source with a 12" wide x 24" long emitter (depending on the fixture, obviously).

The issue with LEDs isn't, unfortunately, all related to intensity or spread. There are simply some corals, most specifically in the acropora genus, that do not do well under the spectrum that current LED fixtures provide. I've experienced this personally - multiple colonies have dramatically color-shifted or STNed/RTNed under my LED fixtures, where frags of those same colonies do quite well under fluorescents. Keep in mind that this is with a great deal of experimentation with altering the actual output spectrum of the LED fixtures within the limits of the spectrum that the included diodes can provide, and with the assistance of PAR meters and a spectroradiometer.

This is antecdotal observation, of course, but there are many others that have experienced something similar. There are plenty of reports with respect to this in the SPS forum that are there for the reading. It is very true that there's a selection process going on - one eventually winds up with species/clades of acropora that will do OK under LED fixtures, because the rest of them die. That's essentially how my DT has wound up - I've found perhaps 7 or 8 colonies that have done fairly well, at the expense of 20 or more that did not (and that did do very well under MH).

[ReefWreak]

Originally Posted by dkeller_nc

Metal halides in fixtures, btw, aren't point sources - they're essentially the equivalent of a light source with a 12" wide x 24" long emitter (depending on the fixture, obviously).

The issue with LEDs isn't, unfortunately, all related to intensity or spread. There are simply some corals, most specifically in the acropora genus, that do not do well under the spectrum that current LED fixtures provide. I've experienced this personally - multiple colonies have dramatically color-shifted or STNed/RTNed under my LED fixtures, where frags of those same colonies do quite well under fluorescents. Keep in mind that this is with a great deal of experimentation with altering the actual output spectrum of the LED fixtures within the limits of the spectrum that the included diodes can provide, and with the assistance of PAR meters and a spectroradiometer.

This is antecdotal observation, of course, but there are many others that have experienced something similar. There are plenty of reports with respect to this in the SPS forum that are there for the reading. It is very true that there's a selection process going on - one eventually winds up with species/clades of acropora that will do OK under LED fixtures, because the rest of them die. That's essentially how my DT has wound up - I've found perhaps 7 or 8 colonies that have done fairly well, at the expense of 20 or more that did not (and that did do very well under MH).

I greatly respect your opinion and observation, and have followed the SPS forum thread closely. I get what you mean about MH in fixtures not being "point sources", but technically, they're still point sources. The discussion about the reflector/fixture is valid, but almost every single application, particularly in that link, uses a reflector, but IES still calls them point source. I'm entirely okay with agreeing to disagree on that point.

I think your observations and theory about LED spectrum isn't wrong. I have generally attributed issues/losses to a complex function of intensity and spectrum (and of course normal hobbyist issues). The issue is we just don't know enough to say specifically why LEDs are having a harder time keeping some (most?) aquarium species. I think we would agree on that last point. We have theories, but I don't think there is sufficient evidence to draw a distinct causation, and to my knowledge there haven't been sufficient tests or evidence to even draw significant correlation. Perhaps there is very specific (hobbyist/anecdotal) evidence demonstrating the spectrum issue versus intensity that I haven't seen.

I have really only had one specific individual acropora (with hobbyist lineage) that absolutely hasn't done well out of maybe 20 or so individual acropora of different species that have gone into my tank, so most of my corals have adapted just fine, and have generally flourished. There are examples of tanks that flourish and tanks that fail with LEDs. That is the tough part of the whole MH vs. LED debate; nailing down exactly why LEDs are generally harder to get "lighting excellence" from versus MH, where tried-and-true and plug-and-play are strong arguments for continuing their use.

[dkeller_nc]

I suspect we're saying something similar with respect to the "point source" definition of MH. There's little doubt that the emitter itself is a point source (though nothing is an absolute point source, of course). But in a fixture with the way that we hobbyists them, they're not. This is in contrast to "modular" LED fixtures. That said, "candy bar" fixtures like the ones made by Orphek's Atlantic are somewhat different, at the cost of accentuating the "disco" effect.

I do wonder if some of the source of the LED vs. MH debate with hobbyists on both sides passionately debating their merits is that the source of corals in the hobby has radically shifted to aquacultured from wild-collected. There is an excellent possibility that some of the "All-LED lighting is definitely suitable" arguments are from keeping corals that have been (purposely or accidentally) selected for suitability. Whereas those that have built their tank's stock with maricultured and/or wild-collected SPS under MH/T5HO have experienced high losses with switching to LEDs, and have therefore concluded that LED-only lighting isn't acceptable.

In other words, it's possible both camps are correct, just not in the way that they think they are.

It's a matter of subjective opinion as to whether light sources that we use over our tanks should be able to support anything and everything, or whether some selection pressure to avoid the pitfalls of traditional lighting is acceptable.