Not liking 10,000K MH bulbs

[DaisyPolyp]

I would love to see some objective analysis done on this topic to finally kill all the rumor/conjecture/speculation that is rampant.

People have tested different lamps over multiple tanks/vats all plumbed together with frags from the same mother colonies in them. It would be nice if someone who's done that could chime-in...

You're right, its called:

Photobehavior of stony corals: responses to light spectra and intensity
O. Levy, Z. Dubinsky and Y. Achituv
Faculty of Life Sciences, Bar-Ilan University, Ramat Gan 52900, Israel
4041 The Journal of Experimental Biology 206, 4041-4049
© 2003 The Company of Biologists Ltd
doi:10.1242/jeb.00622

I quote: "We studied the absorption and the action spectra for photosynthesis and the distribution of zooxanthellae within the corals. We also studied the photosynthetic characteristics of the four species using the
SCUBA-based, fast repetition rate fluorometer (FRRF)"

...in this study O'Levy shows that coral will retract their tenticles to provide maximum exposure to the light source in order to maximize photosynthesis... he goes on to make this conclusion:

"Light at wavelengths in the range 400–520nm was most effective in
eliciting full tentacle contraction"

...these measurements were taken using the Li-Cor LI1800 scanning spectroradiometer, which articles such as the one in AAOL failed to use because of their cost, but it is the only one that measure the lower wavelengths accurately.

 

[Unarce]

Nice! Unfortunately, they'll still see it as an assumption.

I know I repeat a lot of things, but it's all stuff that support the 'theory'. I really hoped to get supporting arguments from this forum but essentially get, '6500K is better. I don't know why, it just is'. I'm only asking for a little more than that (it doesn't have to be as in-depth as DaisyPolyp's). Please don't blame me if the information isn't there. I've searched for the facts to justify warmer kelvin lighting and couldn't find any either.

 

[ChrisRD]

"Light at wavelengths in the range 400–520nm was most effective in eliciting full tentacle contraction".

OK, now go look up the spectral output graphs for some of the popular 10000K German halide lamps and the 6500K Iwasaki lamps. You'll notice they produce a lot of energy in this range...

 

[Unarce]

"Light at wavelengths in the range 400–520nm was most effective in eliciting full tentacle contraction".

OK, now go look up the spectral output graphs for some of the popular 10000K German halide lamps and the 6500K Iwasaki lamps. You'll notice they produce a lot of energy in this range...

I agree with that. In some cases, they put out even more between 400-520nm. The problem is, when it's coupled with strong output of 520-640nm (which is what 6500K and 10000K consist mostly of), it has an adverse effect on photosynthesis. Corals have adapted to utilizing most of what light is filtered through the water, and less of what isn't.

 

[ChrisRD]

I have yet to see a study showing that 20000K reef lighting is superior to the popular 10000K/6500K lamps in this thread. I'm not sure we've even decided on a metric of what constitutes "superior" (growth, coloration, etc.)

If the relationship is so simple and obvious that a monochromatic blue lamp is the "right" one - where is the proof? Where is the hobby-related study that shows this? Questions/issues have been raised regarding other successful forms of lighting - but they're being ignored.

IMO we're all just speculating in this thread. In truth, if there was one "right" type of reef lighting, everyone would be using it. This debate and the "theories" being presented here are nothing new. This is an old, discussion which is likely the reason it won't attract many experienced hobbyists or experts (which is unfortunate).

As I said before, I use 20K lighting myself - I just don't presume to know as much about reef lighting as certain people in this thread. I DO think it's important for people (especially newcomers) reading threads like this to realize that there is a lot more to the story than "20K is the right lighting to use over your reef". IMO that's a drastic oversimplification of the issue.

To clarify, my intention was never to point out that 6500K or 10000K lighting is "better" than 20000K lighting - just that there are countless examples over many years in the hobby of these lighting schemes working very, very well. "Better" is a very subjective concept and IMO depends on what you're after.

The best answer at this point is probably a mix. Actually, mixing these lighting types seems to be getting increasingly popular with experienced hobbyists. The 20000K lamps have a reputation for bringing out color and the higher PAR 6500K/10000K lamps have a reputation for better growth rates. The mix is said to give the best of both worlds.

 

[Unarce]

In truth, if there was one "right" type of reef lighting, everyone would be using it.

Maybe there is. Maybe that's why 14K bulbs are becoming sold out everywhere. I do think that 14K is the best mix. I feel lucky enough to have one in our nano.

 

[ChrisRD]

Or maybe it's the latest fad - this hobby has lots of them.

Or maybe people like the simplicity of having one lighting system rather than having to run supplemental lighting to achieve the look they want.

 

[Unarce]

Or maybe it's the latest fad - this hobby has lots of them.

Or maybe people like the simplicity of having one lighting system rather than having to run supplemental lighting to achieve the look they want.

I agree that a lot of fads are based on assumptions, kind of like the whole DSB fad. In this case, there's a lot of data that legitimize the use of a bluer spectrum.

 

[ChrisRD]

I agree that a lot of fads are based on assumptions, kind of like the whole DSB fad. In this case, there's a lot of data that legitimize the use of a bluer spectrum.

Right, and those assumptions are often based on what's going-on in nature. Stuff like DSBs and plenums are good examples of that.

Do you recall a certain "scientific" salt study not long ago that pointed out which salt mix would produce artificial sea water (ASW) that was the closest match to natural sea water (NSW) parameters? Lots of people decided to give this salt mix a try with disastrous results. Many are back to using the old, "bad" salt mixes with excellent results, despite the fact that they don't match NSW parameters very well...

I'm not disagreeing that light in the bluer end of the spectrum is likely a good thing for our reefs (for reasons you and others have shown). I just don't buy the idea that it HAS to come in the form of a monochromatic blue lamp (ie. 14000K/20000K) that produces nothing but 450nm light.

Even if we're just basing this discussion on the information provided in this thread thus far, it seems obvious that at least part of the violet/green spectrums are important too and other types of lamps can produce a lot of energy in those spectrums (as well as in the blue spectrum).

I could start pasting spectral output curves of various lamps in this thread, but I'm sure you guys know where to find them...

BTW, here's an interesting article by Dana Riddle showing how two very spectrally different lamps produced similar photosynthetic rates: http://www.advancedaquarist.com/issues/feb2002/Feature.htm

From the article: "This experiment’s results suggest information potentially valuable for hobbyists - that rates of photosynthesis were essentially the same under these two distinctly different light sources. Other than aesthetic value, there appears to be no advantage, photosynthetically speaking, in using high Kelvin lamps."

 

[ChrisRD]

BTW, in the article, Dana DOES talk about how some researches have found bluer wavelengths to be more efficient in coral photosynthesis (in fact, Dana has done other research which seems to demonstrate this as well).

However, in the article he states: "To believe that blue (430-480 nm) and red (600- 700 nm) wavelengths are required is only partially true. As Figure 1 demonstrates, a wide range of wavelengths are absorbed by chlorophylls A and C2; however, peridinin and perhaps other photopigments, effectively harvest light energy outside of the range normally associated with photosynthesis."

So, again, it appears there's more to the story than just focusing on 450nm light...

 

[DaisyPolyp]

Absolutely good points. One thing that cannot be overlooked is that while 20K's MAY be better (biologically speaking) for corals, we are talking about man-made aquariums and aesthetics should not be discounted as a major factor in a reefer’s light selection. After all, who cares if you have excellent growth in your corals if you can’t stand to look at your tank.

 

[dkedrowitsch]

DaisyPolyp: Right! And, if you look at my origonal post that started this thread, that was the whole reason for me posting.

I bought That Fish Place branded 10,000K bulbs expecting a bright white/slight blue bulb. Instead I got what looked to me like a 20,000K bulb that when added to my already existing T8 Actinic 420s, made the tank look almost purple!

Next thing you know, we have a debate about what is "better" 20KK bulbs or 10KK and less bulbs. :lol:

Anyway, either the bulbs are starting to break in or I am getting used to them but they seemed to have shifted more white and less blue. Still bluer then I expected but not nearly as bad as when I got them. I think it looks good now.

I do not have any coral yet, as the tank is only about 2 months old or so, but that is certainly the direction I'd like to go. That is why I'm using halides/actinic, so I can try corals when I feel the tank is ready.

So, for anyone who is interested in trying That Fish Place brand 10,000K 175W halide bulbs, they seem to be a little bluer then most, perhaps closer to 12000K. But for the price, I feel I got a good deal. Maybe the color is a good alternative to going all the way to 20,000K if you like the brigher look of 10,000K but want some extra blue. With NO T8 actinics, I think the tank looks great now.

 

[DaisyPolyp]

I think the tank looks great now.

...and that's all that matters. Hey, if someone wants to drop a light-up spongebob doll in their tank because they like the look, more power to em.

 

[Unarce]

Hey, if someone wants to drop a light-up spongebob doll in their tank because they like the look, more power to em.

No harm in that.

This was fun, guys. Neither party has swayed, and if personal preference in spectrum is more important, then nothing else can be said. :wink:

 

[ChrisRD]

DaisyPolyp/Reefnutz,

All the technical/theoretical stuff aside, I was hoping you guys could just answer a couple of quick questions before you go. You never really specified, but I'm interested to know:

How long have you been using metal halide lighting over your reef tanks?

When did you make the switch to 20000K lighting (if you've used anything else)?

What have you observed to be different after the switch from when you were using 10000K or 6500K lighting (or whatever you were using before)?

 

[Unarce]

DaisyPolyp/Reefnutz,

All the technical/theoretical stuff aside, I was hoping you guys could just answer a couple of quick questions before you go. You never really specified, but I'm interested to know:

How long have you been using metal halide lighting over your reef tanks?

When did you make the switch to 20000K lighting (if you've used anything else)?

What have you observed to be different after the switch from when you were using 10000K or 6500K lighting (or whatever you were using before)?

I've utilized higher kelvin ratings probably for the last decade. Particularly fluorescent lighting where more than half the bulbs were actinic and the rest 10K. I had good success at rearing SPS and clams.

I finally jumped to HQI last year, hoping to get better growth out of my tortuosa. I used 6500K (mogul) and 10000K (DE) for several months, but observed accerlerated growth after switching to 20K (6 months ago). In the case of the tortuosa, growth was better at 21" away from the 20K bulb compared to it being 13" away from the 10K. This could be because it's a lagoonal species, but the growth seemed to accelerate in all my other specimens. I could give you a list if it would help.

 

[cdeakle]

I love the XM 20,000k bulbs...

I first started out using the Sunburst 12,000k bulbs and I absolutely hated them. Bad algae growth and corals didn't seem to care much for them.

After I upgraded to the XM 20,000k bulb my corals have opened up and extended further then then I had ever seen them. Not to mention that I love the fact that they are much more blue.

 

[mark78]

I think the reason 6500K's have been said to grow corals faster, is because a 250watt 6500K is likley more lumens then a 10k 250watt bulb.

Color is another story I'm just talking growth rate.

One thing I found off in the research I've been doing, I cannot find and publicied info about lumen output of any bulb higher then 6500K. If you want the lumens of a 6500K bulb well here you go! If you want the lumens of a 20k bulb from the exact same manufacturer, well you can forget it.

 

[Unarce]

I think the reason 6500K's have been said to grow corals faster, is because a 250watt 6500K is likley more lumens then a 10k 250watt bulb.

Color is another story I'm just talking growth rate.

One thing I found off in the research I've been doing, I cannot find and publicied info about lumen output of any bulb higher then 6500K. If you want the lumens of a 6500K bulb well here you go! If you want the lumens of a 20k bulb from the exact same manufacturer, well you can forget it.

Where have you been?8O It's well known on this thread that 6500K has way more lumens (PAR, footcandles) than 20K. There is no direct connection between high PAR, warm kelvin bulbs and accelerated growth.

 

[mark78]

Are we talking about any specific coral needs or HID in general?

There is no direct connection between high PAR, warm kelvin bulbs and accelerated growth.

So if you use the same bulb, a 400w MH won't grow corals any faster then a 175w MH?

Since this is debating high intensity, assume it is a SPS or clam in question, as other LPS types may certainly grow better under lower light conditions.