Little to no true actinic (violet) lighting?

[jedimasterben]

I've been wondering this lately. 430nm is the most active photosynthetic spectra (the peak for chlorophyll a), and falls off sharply after that, reaching near zero at 450nm, which is the typical peak for royal blue LEDs or blue T5 bulbs. Chlorophyll c2 absorbs in the spectrum, but it is present in miniscule numbers compared to chlorophyll a (about a 10:1 ratio of a to c2). This information is not new, either, with a lot of the research coming from the 60s and 70s.

Knowing that, why do people recommend to use little or no actinic lighting (in the 420-430nm range), especially in regards to T5 bulbs? I see people continuously repeating 'true actinic bulbs have little PAR compared to blue bulbs, so just use blue bulbs', so what? PAR (photosynthetically active radiation) is not a useful metric to measure growth potential with, as it simply measures the total amount of photons emitted by a light source. A red bulb or LED will light up a PAR meter, but how efficient will it be in comparison to a blue bulb or LED when it comes to growth in corals, with total PAR being the same between them?

This is where PUR comes in - photosynthetically usable radiation. PUR is a measurement of how PAR should effect growth. In regards to corals, a light emitting more blue spectra will probably have less PAR than a light emitting more red spectra (if power levels are kept the same), but the blue light will be much better for growth.

Can anyone help me in my quest to find more information on this? Or am I just looking at a case of misinformation on a grand scale that PAR is the end-all be-all of lighting?

If I can find more data in my favor, my new array will be loaded with violet - about 33 watts of optical power at 430nm [about 45W/m²] and about 45 watts of optical power at 445-450nm [about 60W/m²], over my 48"x24"x16" tank.

(and please, I'd like to keep this thread as on-topic as possible, so if you have nothing to add other than 'blue lights are better than purple, lulz, n00b', please save it for another thread )

 

[SloppyJ]

Ive been wondering the same thing. I will be following along. All of the ecology classes I've had still haven't answered the question. I am still questioning the use of UV LEDs because everything i've read in my textbooks say that UV light is harmful to coral.

 

[jedimasterben]

Keep in mind that ultraviolet light and violet light are very different spectra - ultraviolet is less than 400nm-ish (some argue it starts at 380nm), violet is 400-440nm. True ultraviolet is harmful to corals in large amounts, but slight amounts of it (think of the amount of UV that a halide bulb emits in the 380nm range) can be somewhat beneficial, but that is for the advanced user in specific scenarios.

 

[Trebor]

So you're saying more actinic, less blue for growth.

 

[jedimasterben]

That is my understanding, yes.

 

[Reefing Madness]

My understaning is, you don't need any Actinic lighting for growth, as the blue spectrum penetrates the water best, and has the best growth. I've got people using 4 lamp T-5's with nothing but Blue lamps, not white light at all. I use 250w 22k Metal Halides with no supps.

 

[jedimasterben]

Yes, I acknowledged that in the first post, I am trying to find out why.

It looks like peridinin works with chlorophyll a lot closer than I first though, within PCP bonds it transfers 50-100% of all the energy absorbed (450-480nm) straight into chlorophyll a.

 

[Reefing Madness]

Yes, I acknowledged that in the first post, I am trying to find out why.

It looks like peridinin works with chlorophyll a lot closer than I first though, within PCP bonds it transfers 50-100% of all the energy absorbed (450-480nm) straight into chlorophyll a.

Understood.

 

[Davesgt]

Im following this thread also. Alot of things i still dont understand that id like to know about different spectrums. I do know i use to run 2- AquaBlue Specials and 2- Blue+ and got ok growth, but about 8 months ago i decided to try a combo i saw on another show tank that had the color i was looking for. I switched to 1-AquaBlue Special and 3 Blue+ and for some reason my corals seem to like this alot more and grow alot quiker, as to the point of actually every few days being able to noticeable be able to point out growth. Why it worked idk but i like it lol

 

[bct15]

I don use any true acinic on my tank and get good color and growth out of all types of coral. I use two blue+ and 2x250w 15k mh but am switching to 20k mh very soon.

I don't have any research or journal articles to back up my bulbs, just what others have used that seems to work.

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[larangcon]

interesting, following along

 

[mcarroll]

"True actinic" is often used with the same slack as "full spectrum".

Actinic doesn't have a connotation of any particular wavelength - just that the light in question causes some effect. True whether you're talking Aquariums or photography.

As for logic of the enquiry, a higher percentage of 420nm light penetrates water than any other wavelength we're interested in. It stands to reason coral and their supporting cast have thoroughly (if imperfectly) adapted to this truth.

I would expect this adaptation to be be more true for deep water specimens than others. (I think this adaptation may be more or less true for an individual or colony vs any whole specie or genera.)

Now whether this high-violet/low visibility environment is optimal for the coral is a different question entirely but I'm not sure we have good a way to assess this. Kinda like trying to assess "happiness" if you will.

How can we gauge this?

Growth is the only reliable factor we really have to assert "positive results" and we know our corals are apparently not limited by the relative lack of 430nm light.

Sexual reproduction is another factor we could look at, but essentially nobody gets their corals to reproduce this way. So outside of maybe achieving sexual reproduction it's not going to be a useful gauge. Even if achieved my guess is that there will be other factors which will also figure in heavily.

The last factor I can think of is coloration. In some areas such as fish breeding, garish coloration can be a sign of intense health and "happiness". (In this case, usually followed closely by sexual reproduction.) However, currently we tend to approach coral color more like the GloFish people where it's a decorative or aesthetic consideration that's disconnected with "nature". As there is a lack of understanding (perhaps even a lack of meaning) with respect to coloration in corals, this also may not be a useful gauge.

I also intend to experiment with ~420nm light due to its relatively unique character in water but don't yet know what, if anything, to expect.

Interesting topic to explore!

-Matt


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[Swine]

I like this topic because its not just a "I do this because it works" Its more like.. I do this because science said so haha

So what wave length is going to bleech corals? Could too much blue bleech them more easily?

It makes sense that blue makes it through the water best because it along with violet is the closest to UV in the electro magnetic spectrum.

I'm about to add 14 more LEDs to my custom lights and am trying to figure out the best combination of making the colors pop and growth.

 

[Zack]

Loving the thread, more,more,more!!

 

[Jason_R]

I've been in the hobby a long time. I don't have a background in photosynthesis study, biology, or anything of that nature. What I do know is that early on, people didn't have the large selection of metal halide, T5 and LED lights that we do now. Some people would put halogen lights and other "shop lights" over their tanks to mimic sunlight. Over time, some people were more successful than others. An article in FAMA magazine showed julian Sprung having success keeping one species of SPS using an Iwasaki 150w metal halide bulb. The Iwasaki was actually a sodium vapor bulb made for things like parking lot lights. In general, Iwasaki lights had very high PAR values compared with other bulbs. I believe, as it turns out, Iwasakis are very powerful in all of the visible light spectrum, including the blue spectrum that is used for photosynthesis, it just appears very yellow to us because it emits even more powerful red and green spectrum light.

The Iwasakis were extremely popular in the late 90's. People who had the "best" lighting at the time used a 400w Iwasaki and then used VHO actinic T12's to make it more visually pleasing. The tanks would run great with or without the T12 actinics, because the Iwasakis already covered the spectrum the corals needed.

I don't know if I have my history 100% correct, thats just how I remember it. Long-story-short, I think the reef community started out with the belief that PAR value was important because of the success of the Iwasakis, and perhaps it still sticks today.

 

[Jason_R]

I also need to point out that the corals we keep today are a little different in 2013 than they were in 1998. In 1998, if you got an acro colony, chances were that it was picked directly off a reef, in very shallow water, sometimes at low tide where the coral was exposed. The colonies from the wild were used to very high lighting intensities. These corals would have browned out and perhaps died under VHO intensity.

As time went on, people started growing and fragging these corals. Coral "farms" started cropping up, and we saw people having more and more success keeping SPS under VHO and later HO florescent tubes. I think we have a much bigger selection of stony corals that can survive and thrive under lights of lower intensity than we did 14-15 years ago.

 

[Butcher333]

I was super exited to see this topic but curious of any follow up. Hmmm! I think 400-440 is important.