Not liking 10,000K MH bulbs

[ChrisRD]

My $0.02 (again )...

The Dana Riddle study on the previous page basically showed that photosynthetic activity in corals was independent of spectral quality and a function of overall intensity.

I've yet to see in this thread, or anywhere, a similar study that shows a monochromatic blue lamp outperforming a wider spectrum lamp of equivalent PAR. I'm not saying it couldn't happen - I've just never seen the study.

Of course another one of his studies showed that spectrum had a very pronounced effect on coral coloration. It also showed that, if isolated, certain spectrums are probably more important to photosynthesis. He also mentioned that corals can utilize wavelengths outside that optimum range for photosynthesis, which (to me anyway) is what complicates this whole thing...

So in other words - according to Dana's work, if you had a 250 watt 6500K Iwasaki lamp (high PAR) over the same corals, at the same height, in a similar reflector as 250 watt 20000K Radium (predominantly 450 nm wavelength output) you should see faster growth under the Iwasaki and better colors under the Radium.

This is exactly what many (but apparently not all ) hobbyists that have tried these lamps appear to report for results (at least in the context of SPS corals). This is also the rationale (in recent years) for combining lighting types - to get the best of both worlds.

Of course a lot of people get the PAR they need for good growth with the 20000K lamps by going up to high enough wattage and/or getting the corals close enough to the lamps and, again, basically get the best of both worlds.

 

[Anonymous]

Look at Fenners Conscientious Marine Aquarist. His parts on lighting shows a mix of 65K and 20K halides as the best asthetic mix. In that case you get the best of both worlds. Asthetics and quality wavelengths.

 

[Unarce]

My $0.02 (again )...

The Dana Riddle study on the previous page basically showed that photosynthetic activity in corals was independent of spectral quality and a function of overall intensity.

I've yet to see in this thread, or anywhere, a similar study that shows a monochromatic blue lamp outperforming a wider spectrum lamp of equivalent PAR. I'm not saying it couldn't happen - I've just never seen the study.

Of course another one of his studies showed that spectrum had a very pronounced effect on coral coloration. It also showed that, if isolated, certain spectrums are probably more important to photosynthesis. He also mentioned that corals can utilize wavelengths outside that optimum range for photosynthesis, which (to me anyway) is what complicates this whole thing...

So in other words - according to Dana's work, if you had a 250 watt 6500K Iwasaki lamp (high PAR) over the same corals, at the same height, in a similar reflector as 250 watt 20000K Radium (predominantly 450 nm wavelength output) you should see faster growth under the Iwasaki and better colors under the Radium.

This is exactly what many (but apparently not all ) hobbyists that have tried these lamps appear to report for results (at least in the context of SPS corals). This is also the rationale (in recent years) for combining lighting types - to get the best of both worlds.

Of course a lot of people get the PAR they need for good growth with the 20000K lamps by going up to high enough wattage and/or getting the corals close enough to the lamps and, again, basically get the best of both worlds.

I'm familiar with Mr. Riddle's work. Again, what's missing is the connection. He assumes that corals can utilize wavelengths outside that optimum range for photosynthesis, but can't explain how or why. I don't doubt that his study and the results of many others have gotten great growth out of these bulbs, but you have to admit that there's a strong possibilty of another aspect other then the warmer spectrum itself since it cannot be explained. For instance, when DaisyPolyp pointed out increased planktonic growth. Phytoplankton, and other algae/protozoa (hair, dinoflagellates, cyano) thrive on low kelvin lighting. There's at least the connection that the corals could be getting the majority of their carbon energy through feeding instead of the high intensity light itself.

It's just not a good enough reason to say 6500K or 10000K is better simply because it might grow corals faster. Corals can grow faster from increased temperature; a healthy planktonic population; heavier water flow. I'm not bashing the use of 6500K or 10000K, but for good reason, most people use 6500K or 10000K with actinics. Maybe it's just for appearance (we're not in this to raise ugly looking corals), but corals greatly benefit from it. What cannot be denied is that the bluer spectrum best simulates the natural reef. In terms of lighting, this is best for overall growth, coloration, and health of the coral. There's no better reason than that.

 

[mark78]

I'm not trying to make the point that a 6500 is better then a 10000k, only that the 6500 would be more intense, thus giving the illusion your corals are growing faster due to the light color, when its really the intensity.

I don't belive corals only use the blue light. If this was the case, then we could all be using actinics to grow our corals. Photosynthisis is photosynthisis, the zooxanthalle(sp) in the corals should be using a broad range of light. Unfortunalty I have no "proof" to offer twords this. Anthony made a statement in his book about 6500's and what I am talking about, but I had borrowed it and can't go look it up now

terestial plants are similar to corals, blue colored bulbs will promote vegitive growth (chlorophyl) while a more red color bulb will do better at promoting flowering. I know there are differences and you cannot compare a coral to a plant...but...chlorophyl = green, zooxanthle (usually)= coincidence?

This will be debated for years but at least its fun

 

[Unarce]

I don't belive corals only use the blue light. If this was the case, then we could all be using actinics to grow our corals. Photosynthisis is photosynthisis, the zooxanthalle(sp) in the corals should be using a broad range of light. Unfortunalty I have no "proof" to offer twords this. Anthony made a statement in his book about 6500's and what I am talking about, but I had borrowed it and can't go look it up now

terestial plants are similar to corals, blue colored bulbs will promote vegitive growth (chlorophyl) while a more red color bulb will do better at promoting flowering. I know there are differences and you cannot compare a coral to a plant...but...chlorophyl = green, zooxanthle (usually)= coincidence?

This will be debated for years but at least its fun

No one ever said it's just blue light. The red spectrum has a narrow peak for photosynthesis too. Please see the chart of what spectrum corals utilize most for photosynthesis. It's when the light in intensified to full-spectrum that photosynthesis actually slows down. Since zooxanthellae cannot photosynthesize at its peak, this might explain the drab coloration under 6500K. If 6500K increases planktonic reproduction, than a lot of the corals carbon energy is met through feeding. The feeding can provide more energy for calcification which leads to faster growth. This could be the indirect connection between high intensity lighting and increased growth.

 

[DaisyPolyp]

It's when the light in intensified to full-spectrum that photosynthesis actually slows down.

...this cues me for another chart! :wink:

you'll notice how these 3 species slow down their photosynthesis in response to middle-of-the-day light. This is from a study taken In Situ at heron island, great barrier reef.

 

[ChrisRD]

Those charts show photosynthetic activity slowing at very high intensities. Not sure how you're making the connection to spectrum here. How much does the spectrum really change throughout the day under 30' of water?

And again, looking at that action spectrum chart above and comparing it to spectral curves for 10000K lamps it appears that they'd actually do a better job of covering the area under that curve than the narrow spike shown at 450 nm on most spectral charts for 20000Ks.

I think at this point you guys might actually be proving the case for 10000Ks...

 

[DaisyPolyp]

Those charts show photosynthetic activity slowing at very high intensities. Not sure how you're making the connection to spectrum here. How much does the spectrum really change throughout the day under 30' of water?

Actually, the water depth for the study ranged from 0.27m to 2.78m as the researchers were trying to mitigate the effect of attenuation of light through seawater.

I don't know if you've ever seen a sunrise or sunset at the GBR, but suffice it to say that the spectrum is radically different than midday (bluer in the morning as coincides with the chart, and red/orange in the evening).

 

[ChrisRD]

Here are the spectral curves from one of Sanjay's studies. These are 150 watt DE lamps. One is the AB 10K and the other is the BLV 20K.

Compare the area under the curves for these two lamps in the 400 nm - 520 nm range that was cited (in that study earlier in this thread) as the optimum spectral range for coral photosynthesis. I'd say the 10K wins hands down.

 

[ChrisRD]

I don't know if you've ever seen a sunrise or sunset at the GBR, but suffice it to say that the spectrum is radically different than midday (bluer in the morning as coincides with the chart, and red/orange in the evening).

Again, I don't see the chart making reference to spectrum, just intensity. What was the conclusion of the study?

 

[DaisyPolyp]

the 10K's do have the blue spike, no doubt, but 20K's are really varied depending on the manufacturer. Example - Radium 20K vs. XM 20K very different results. I'm not familiar with the BLV, but I have not heard it to be one of the recommended 20K's. FWIW, reefnutz and I both like the XM's.

(of course I'll see if i can dig up the radium vs. XM chart)

 

[DaisyPolyp]

here ya go.... this is also from Sanjay's study :wink:

notice how the 10K HQI differs greatly with the 10K coralife... in this analysis it appears that the 20K coralife wins easily.

 

[ChrisRD]

the 10K's do have the blue spike, no doubt, but 20K's are really varied depending on the manufacturer.

Actually, they don't. They all seem to have that very narrow spike at 450 nm and not much else...

Example - Radium 20K vs. XM 20K very different results.

Actually, the spectral curves for the 20K XMs and the Radiums are extremely similar.

 

[ChrisRD]

notice how the 10K HQI differs greatly with the 10K coralife... in this analysis it appears that the 20K coralife wins easily.

Against what? Not the 10K HQI lamp or the 6.5K Iwasaki...

 

[ChrisRD]

notice how the 10K HQI differs greatly with the 10K coralife...

I'm not sure what you're trying to point out, but FWIW, the Coralife 10Ks and the Blueline 10Ks are really not 10K lamps. They are both very monochromatic, blue and dim (basically 20Ks).

True 10K lamps like the XMs, Ushios, BLVs, ABs, etc. all have similar output curves to what Sanjay is showing as the 10K HQI in this chart - large peak at around 420 nm with most of the overall output in the violet/blue/green range (which is ideal for photosynthesis according to the studies you've cited BTW )

 

[Unarce]

Those charts show photosynthetic activity slowing at very high intensities. Not sure how you're making the connection to spectrum here. How much does the spectrum really change throughout the day under 30' of water?

It actually changes quite a bit. The chart shows 3 species of Acropora, Goniastrea, and Porites each displayed the decline in electron transport rate (photosythetic activity) during the point of highest light. A point which you consider to be between 6500K and 10000K.

 

[krullulon]

on a slightly off recent-topic note (but on-topic for the original post), i just switched-out my ushio 250W 10k for an XM 250W 10k and holy cow the XMs are so much more appealing visually! the XMs also have about 20% higher PAR on a ballast-per-ballast comparison with the ushios, but i don't know what the spectral output is... does anyone have the XM data?

 

[ChrisRD]

It actually changes quite a bit.

OK, even if we accept the idea that the spectrum is also changing and having an effect on photosynthesis (along with intensity) - how do you know what component of the resulting decrease in photosynthesis is spectrally based and what component is intensity based?

Riddle's study isolated intensity so the variable was spectrum and it didn't seem to make a difference in photosynthetic rates.

Again, even putting that aside and going with the numbers shown in the study Daisy cited earlier (that 400 nm - 520 nm light is most important in coral photosynthesis), the 10K lamps look like they're fairing better in the spectral curves (more area under the curve in that range than the 20K lamps)...

The chart shows 3 species of Acropora, Goniastrea, and Porites each displayed the decline in electron transport rate (photosythetic activity) during the point of highest light. A point which you consider to be between 6500K and 10000K.

I don't understand what you're saying here. Are you saying you think that at peak intensities in this study the spectrum present was similar to a 6500K or 10000K halide lamp? How do we know this without that information being presented in the study?

 

[ChrisRD]

on a slightly off recent-topic note (but on-topic for the original post), i just switched-out my ushio 250W 10k for an XM 250W 10k and holy cow the XMs are so much more appealing visually! the XMs also have about 20% higher PAR on a ballast-per-ballast comparison with the ushios, but i don't know what the spectral output is... does anyone have the XM data?

XM has it right on their site. http://www.xmlighting.com/images/250w10kspectrumMogul.jpg

 

[DaisyPolyp]

Again, even putting that aside and going with the numbers shown in the study Daisy cited earlier (that 400 nm - 520 nm light is most important in coral photosynthesis)

Actually, the quote was that the 400-520 range is most effective in elliciting tenticle retraction (a function of the coral's tissue), I stated before that 440-480 was the most important in coral photosynthesis (a function of the zooxanthellae). The coral doesn't want to get in the way of the light needed for the zooxanthellae, so it contracts before the optimal time and expands after the optimal time. referencing back to the chart you see that 400nm and 520nm are not anywhere near the peak spectrum shown for photosynthesis.