Spectrum vs. PAR

[-JB]

Looking at the links provided. I understand where you are coming from.

But right now PAR is the best understanding of what will fuel the most growth of corals. I'm going to assume based on your link and the high Kelvin lamps we are taking about, we want to limit the discussion to Acroporidae corals.

Iwasaki lamps provide the most growth that we have seen. Radium and other blue lamps seem to provide the best color. IMO any discussions we are having are for the eye of the beholder. Because the Iwasaki provides more than enough growth for the average consumer as well as the a coral farmer. The main objective then, seems to be how to get good growth as well as the striking colors that are so high in demand.

IMO PAR still plays a big role in determining this. And looking at the spectrum distribution graphs you have linked to from Tyree, it shows how seriously lacking the current blue bulbs are.

Radium/xm type blue bulbs provide almost all their intensity in one small band 450nm, and two other bands, 412nm and 546nm. Both these other two bands are aprox. 25% and 19% the intensity of the 450nm band. Still this is only three bands in the entire spectrum. The rest of the spectrum, not including those three mentioned, irradiate only about 11% in the radium and 3% in the XM, of the intensity of that 450nm peak.

Now if you look at the Iwasaki, it's two peaks in the 400-500nm range are at 420nm and 490nm. but the average of almost the entire band from 400-500nm is about 80% of the peak value seen at 420nm. With the lowest point of the Iwasaki being 40% of the peak at 420nm.

Yes a combination of PAR and spectrum would allow one to choose the lamp that had a high PAR rating as well as a spectrum that matches best what corals need to have good growth as well as the coloration we so like to have. I also think the PAR of the lamp is very helpful as the human eye is a poor determination of overall intensity, as seen in the Iwasaki lamp. The Iwasaki has lots of blue in it. Unfortunately our eyes tend to give more weight to the greens and yellow making the bulb not as attractive visually, even though it does a fine job of satisfying the needs of the coral it is placed over.

But the PAR reading if very useful. As just the spectrum graph helps little in understanding the overall intensity of the lamp. This can only be measured in terms of PAR

 

[Anonymous]

Excellent points, -JB! "The eye of the beholder" is the eye of a terrestrial being whose life depends upon being able to see particular colors! I think this one should be..
Marked for archiving

 

[Unarce]

JB,

Thanks for expressing your take on the subject. I acknowledge that PAR and Spectrum each play a significant role, but I can't seem to locate any research or evidence showing that SPS corals grow faster under Iwasaki's.

If Peter Ralph's research is true, could the abundance of the 500-650nm range of an Iwasaki bulb hold back the zooxanthellae's full potential in generating photosynthetic energy?

I don't mean to be stubborn. There's a couple of things that I do out of the norm with my reef and have always relied more on facts rather than hobby trends. There are also several distributors whose opinions I respect very much that prefer 20K or Radiums as well. Although, that could be more for the better coloring.

Thanks again.

 

[-JB]

I do not know if anyone has ever done a study to prove that Iwasaki grows coral fastest. I do know more than a few people who have switched from Iwasaki to radium then back to Iwasaki purely due to the lack of growth they experienced. IIRC those who switched back were people who were attempting to cultivate SPS. I know some of the coral farmers who use the radium/XM bulbs due it for the colors they get, rather than the growth. Although I have heard of very good growth in shallow tanks when using blue bulbs. That would also tend to show that the PAR has a lot to do with growth as the shallow water tend to allow a higher PAR from an otherwise dim bulb.

I'll be testing this idea myself in the near future as I intend to set up a cultivation tank with only 7" of water and use an XM20K lamp for lighting, hopefully getting strong growth and good coloration.

 

[MiNdErAsR]

Stimulating photosynthesis should be the primary goal for reef lighting, and if you read the research links I provided, you'll see that it points to spectrum rather than PAR for maximum energy.

Seems to me you're comparing apples to oranges here. If I read your link correctly, the tests were conducted under natural sunlight. How could you possibly carry over anything from this to aquarium lighting, where intensity is no where near sunlight? However, a similar study under various halide bulbs might be a worth while endeavor.

 

[Unarce]

You're still fixated on intensity. I'm pointing out the importance of spectrum. What you would expect is full-spectrum at midday, and lower PAR the rest of the time. Just like the dawn to dusk effect so many apply in reefs. As we mentioned many times previously, we all know we couldn't possibly match the suns intensity, but how many reefers do you know have a reef that's 50' deep. The research just shows that there could be less need for the 500-650 wavelength.

 

[MiNdErAsR]

The article by Richard Harker points out the dawn/dusk effect so many apply is needless. FWIW, in my system there is only a 15 minute difference between PC's turning on/off over the halides. I look at it as a small courtesy offered to the fish.

Perhaps when intensity is so great then spectrum would play a more important role, but since intensity is lacking in our systems we look to PAR to pick up the slack? Another fwiw, my tank never looked better then when I was running dual 250w Iwaskis with dual 110w VHO actinics. I'm seriously considering returning to that setup over my current one, which is an AB Aquaspace light (dual 250w DE and dual PC).

I'd love to hear from both Richard Harker and Sanjay Joshi on this thread.

 

[Unarce]

Again, not really looking for opinions. Just hard data. Hopefully, JB's research can prove it wrong than we can all go back to Iwasaki's.

 

[ChrisRD]

FWIW, here's a little exerpt from Sanjay's 250 watt lamp study:

"If you subscribe to the “more PAR is better” theory, then obviously the best choice is either the double-ended 10,000 K lamp or the 6500 K Iwasaki lamp. If you subscribe to the “more blue is better because corals are found in water where the higher wavelengths are filtered out” theory, then it’s worth noting that the 6500 K Iwasaki lamp had higher output in the violet/blue range than the 10,000 and 20,000 K Coralife lamps. The double-ended 10,000 K lamp is the best combination, offering both the best PPFD and the more blue color many reef hobbyists are interested in"

 

[Unarce]

Mr. Joshi's statement seems to contradict the diagram he charted himself along with Dave Morgan. Maybe we'll never know the truth.

I do agree with the 10K DE which I still use myself. Although my wife hates how it lights up the whole dining room.

 

[Anonymous]

Heh.. well.. it is the SUN you're trying to mimic, ain't it? :lol:

 

[ChrisRD]

Mr. Joshi's statement seems to contradict the diagram he charted himself along with Dave Morgan. Maybe we'll never know the truth.

Which part of his statement contradicts the diagram?

 

[Unarce]

The chart shows that both the 10K and 20K have more blue.

 

[ChrisRD]

It's hard to see it in Chart 2, but in Chart 4 it's obvious that the Iwasaki has a higher peak in the blue range than the 10K and just slightly less than the 20K.

However, Sanjay's statement was:
"...the 6500 K Iwasaki lamp had higher output in the violet/blue range than the 10,000 and 20,000 K Coralife lamps"...

It has a much higher peak in the violet range than either the 10K or 20K. It has a higher peak in the blue than the 10K and just slightly less than the 20K. I believe that's why he said "violet/blue" range. He seems to be referring to that whole range in which case, his statement seems accurate to me.

Also, I think total output in a given range would be the area under the curve, not just the height of a peak in a certain wavelength...

 

[Unarce]

Thanks for clearing that up ChrisRD.

I do think we're getting away from what was originally discussed. It's clear that the peak levels for photosynthesis for corals are in the blue and red range. The research also indicates that exposure to full spectrum (midday) showed a decline in photosynthetic activity.

Full spectrum doesn't seem necessary and could actually be a hindrance. On top of that, it's unattractive (unless you add actinic supplementation) and seems to generate more heat (shelling out more for fans or a chiller).

There could be a million posts of opinions stating that "more PAR is better" but there's still no proof or research showing why or if it even is.

That's all I'm hoping for.

 

[ChrisRD]

Thanks for clearing that up ChrisRD.

Hey - don't mention it. Of course, I have no idea what it all means - just reading off the chart...LOL.

I do think we're getting away from what was originally discussed.

In my first post I was just trying to show that there appears to be some lamp choices that cover both concerns (PAR & spectrum).

 

[Unarce]

Sorry ChrisRD,

That last one wasn't really directed to you. It seems difficult for some to look beyond 'intensity'.

 

[-JB]

There could be a million posts of opinions stating that "more PAR is better" but there's still no proof or research showing why or if it even is.

That's all I'm hoping for.

I still think PAR will be very useful in the long term. Even if it comes out that the low end of the spectrum plays a major role in growth or coloration of the coral. You need a way to measure it. This is PAR. Two lamps can have the same spectral curve and be of the same wattage can still have very different PAR readings. All things being equal, the one with the highest PAR in this case would be better for the coral (unless we find a saturation point of PAR, but that hasn't happened yet). Even looking at the Radiumin Sanjay's testing over time it is not the spectrum that shifts, rather, it is the intensity of the spectrum that diminishes. That is measured as PAR.

 

[Unarce]

It's been agreed that PAR is useful for measurement.

It still doesn't prove the need for higher PAR, full-spectrum lighting.

http://www.science.uts.edu.au/des/Staff ... hesis.html

You have to wonder to some degree, if it has a negative effect on photosynthesis.

 

[-JB]

But are you taking into consideration that acropora in our tanks receive little care the same as on a real reef. That link shows that those acropora studied, received enough light in nature that photosynthesis can shut down in the mid afternoon. But in the wild, acropora do not solely receive there daily nutrition through photosynthesis alone. If I remember correctly, I think the value was extremely high, as quoted by Eric Borneman, somewhere in the realm of 70% of the daily nutrition of acropora comes from food captured by the polyps. In our tanks almost no part of the coral is satisfied in this way. Might this have some bearing on the amount of additional light they might need in our tanks? (I don't know the answer)

I also don't see the correlation you are making that higher spectrum lighting is causing the coral to shut down prematurely.