Is there any Value to UV-A lighting

[Ubergroover]

I have seen several product reviews that seem to hint at the UV spectrum could be beneficial to coral. Does anyone have any info or first hand experience?

Thanks!

 

[P-Dub]

See this...
https://www.reef2reef.com/threads/how-important-is-uv.229487/
The short answer is yes, with the caveat being true UV is not possible unless MH's are used. Still, the "UV" spectrum provided by the majority of today's LED's is very beneficial.

 

[KrisReef]

I love this question and I don’t know the answer. I believe that coral symbionts can use UV for photosynthesis, but I do wonder about coral bleaching / burning under LEDs and if there is a link?

 

[hart24601]

See this...
https://www.reef2reef.com/threads/how-important-is-uv.229487/
The short answer is yes, with the caveat being true UV is not possible unless MH's are used. Still, the "UV" spectrum provided by the majority of today's LED's is very beneficial.

How is true UV not possible if using LEDs? By definition anything under 400nm is UV and at least kessil and orphek have diodes under 400nm.

 

[Ubergroover]

See this...
https://www.reef2reef.com/threads/how-important-is-uv.229487/
The short answer is yes, with the caveat being true UV is not possible unless MH's are used. Still, the "UV" spectrum provided by the majority of today's LED's is very beneficial.

that was a good tip...Thanks for the link!

 

[P-Dub]

that was a good tip...Thanks for the link!

We're here for you...

 

[P-Dub]

How is true UV not possible if using LEDs? By definition anything under 400nm is UV and at least kessil and orphek have diodes under 400nm.

@hart24601 300-400 is accurately defined as Near UV or NUV and true UV light encompasses both UVA and UVB. For practical purposes of recreating lighting available on the natural reef, UVA and UVB will be required for true UV lighting. That is not possible with LED lighting available for reef aquariums.

 

[hart24601]

@hart24601 300-400 is accurately defined as Near UV or NUV and true UV light encompasses both UVA and UVB. For practical purposes of recreating lighting available on the natural reef, UVA and UVB will be required for true UV lighting. That is not possible with LED lighting available for reef aquariums.

Do you happen to have a chart showing UV penetration by depth in the ocean? Seems hard to think UVB would make it to corals we commonly keep. @Dana Riddle

 

[P-Dub]

Do you happen to have a chart showing UV penetration by depth in the ocean? Seems hard to think UVB would make it to corals we commonly keep.

@hart24601 Here is a good read for you...
https://www.int-res.com/articles/meps/144/m144p109.pdf

 

[P-Dub]

@hart24601 Also, this where pg.2 has a graph for you...
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.867.7964&rep=rep1&type=pdf

 

[jda]

MH has plenty of UVA. Some T5 have a lot too - Actinic for starters. Some LED panels do. True UV didoes are expensive, do not last long and will not pop on a PAR meter - we heard at MACNA a few years back from a very large LED manufacturer that they will not include them since it changes their PAR to watt numbers even though the corals will probably benefit.

UVB is not much of a concern and the glass in MH fixtures will filter it out. MH fixtures without the glass can cause UV damage. There is UVA down to about 350 in most MH bulbs and it is useful. It penetrates up to 10m in the ocean in a typical reef environment, but this is highly variable upon how clear the water is - remember that most everything that we have in this hobby is collected on one breath... not all, but most. There are plenty of lagunal, atoll and even open reef corals that are in the sun or just a few inches below the surface at low tide and they are certainly getting UVA and UVB and they deal with it.

UVA has more energy than other light spectrum. There are a lot of different proteins that can get energy from this spectrum. Corals can use some of it and spit the rest out at higher energy. For example, 360nm is invisible, but say a coral uses some of that energy and then spits it back out at 405nm, then that is a beautiful violet. Some corals make colorful pigments to act as UV sunscreen.

In short, it can make a difference. Do you need it? Not for everything, IMO, but it helps with some. It is one of the reasons that many speculate that LED still cannot do what T5 and MH can do.

 

[hart24601]

Know of any studies looking at coral response to UV light only (no other spectrum) at the intensity UV is found on an average reef?

 

[Rpc07]

Interesting discussion, following along.

 

[Gareth elliott]

How much uv actually reaches the corals in the wild? There is a lot of interference on the surface near the coast that is going to filter more of it out at than open ocean. And even a basic white led or cfl will produce a small amount of uv. Speaking in terms of humans we require so little UVB that our weekly requirement is something like 15 minutes outside in indirect sunlight. Also how much is reflected via fluorescence of the organism acting as a sunblock?

 

[P-Dub]

Know of any studies looking at coral response to UV light only (no other spectrum) at the intensity UV is found on an average reef?

None that I know of. I'm not certain that there would be any meaningful data derived from such a study hence the likely lack of any data readily available.

 

[hart24601]

None that I know of. I'm not certain that there would be any meaningful data derived from such a study hence the likely lack of any data readily available.

I think it would be meaningful to see at what intensity corals respond, if any, to UVA light and at what wavelengths. It seems hard to support needing UV without evidence it's beneficial, particularly below 380. I can see the 380 to 400 being utilized but it would be interesting to see other wavelengths and then ideally to see at what intensity they produce response from corals, what that response it and if it occurs with levels found on reefs. If I am reading that paper correctly it says at 3m deep (~10ft) at 12-12:30 300-320nm was 0.46 W m-2, while the entire UV spectrum was 15 W m-2 from 300-400. Of course that is at a pretty intense time of day so it wouldn't be that high for long. Looks like the PAR at that level was 759 or (188 W m-2).

Interesting stuff. I am not sure if I have seen much that would lead me to think and LED system like orphek with 380nm diodes. Kessil does produce 2 entire lights with only UV for research, however it's hard to think they didn't put those same diodes in their fixtures since most tests show some UV (370 and 390):

http://kessil.com/photoredox/Products.php

Now how much these light produce vs/a reef and how much is beneficial is what I am curious about. I did see the huge swatch of bleached coral when the glass shield on the MH on the NY aquarium broke so it seems pretty easy to get too much. Clearly those LEDs put out just a tiny bit of UV but do we know they should be putting out more for optimal coral health?

 

[P-Dub]

I like your thinking however utilizing UV wavelengths only would result in certain death of the coral. You are starving the symbiotic algae vital for coral health by removing its energy source. Studies have been done to determine the necessity of UVA & UVB wavelengths and at what point they become detrimental. Clearly, corals can grow and survive quite well without UV. What UV and what levels of that particular UV spectrum produce what results in corals we keep, remains to be seen. Primarily, it seems, UV plays a role in coloration and fluorescing pigmentation in out captive corals. It would be interesting to see what particular wavelength yields what color morphs. I have the whole back of my 6-foot tank illuminated by Orphek bars with 1 "UV" diode for every 2 blue. The coloration between two identical corals of roughly the same age and depth within the aquarium is dramatic.
The photo below is of a frag near the front of the tank lit primarily by SB 16" basics with little light from the Orphek bars.

Same type of coral from the same mother colony located approximately 1 inch deeper but flooded with the Orphek bars and just to the left of a BlazeXmini and under a SBreef Lights16" basic.

Dramatic.

 

[jda]

The sun produces it. It gets to the corals. All true science trusts nature until it is proven to be wrong, not the other way around. IMO, this is why LED tech and some reefers do not go as far as they can since in an industry where proof of anything is nearly non existent, they take pieces and parts of this or that and conclude that some part of the nature are not beneficial. It is pseudoscience.

Then, forget about studies or tests for a minute. What anecdotes and evidence have you seen that suggest that UV in not important? Is there any coincidence that the light source that creates the most UV also performs the best over corals? Nope. Is there any evidence that adding light sources with UV (T5s) to help those that do not have it (LEDs) have been beneficial? For sure.

...so assume that all wavelengths are beneficial from 350 to 850nm, like prior research has shown... which also support nature. If you want work to discredit this, but it will be nearly impossible since only a few publications (think advertising) from some LED manufacturers have ever said otherwise.

 

[P-Dub]

The sun produces it. It gets to the corals. All true science trusts nature until it is proven to be wrong, not the other way around. IMO, this is why LED tech and some reefers do not go as far as they can since in an industry where proof of anything is nearly non existent, they take pieces and parts of this or that and conclude that some part of the nature are not beneficial. It is pseudoscience.

Then, forget about studies or tests for a minute. What anecdotes and evidence have you seen that suggest that UV in not important? Is there any coincidence that the light source that creates the most UV also performs the best over corals? Nope. Is there any evidence that adding light sources with UV (T5s) to help those that do not have it (LEDs) have been beneficial? For sure.

...so assume that all wavelengths are beneficial from 350 to 850nm, like prior research has shown... which also support nature. If you want work to discredit this, but it will be nearly impossible since only a few publications (think advertising) from some LED manufacturers have ever said otherwise.

I'm not following your query regarding evidence that suggests UV is not important?
*EDIT: I see now, response to post #16.

 

[hart24601]

The sun produces it. It gets to the corals. All true science trusts nature until it is proven to be wrong, not the other way around. IMO, this is why LED tech and some reefers do not go as far as they can since in an industry where proof of anything is nearly non existent, they take pieces and parts of this or that and conclude that some part of the nature are not beneficial. It is pseudoscience.

Then, forget about studies or tests for a minute. What anecdotes and evidence have you seen that suggest that UV in not important? Is there any coincidence that the light source that creates the most UV also performs the best over corals? Nope. Is there any evidence that adding light sources with UV (T5s) to help those that do not have it (LEDs) have been beneficial? For sure.

...so assume that all wavelengths are beneficial from 350 to 850nm, like prior research has shown... which also support nature. If you want work to discredit this, but it will be nearly impossible since only a few publications (think advertising) from some LED manufacturers have ever said otherwise.

I just would like to see some studies with coral and their response to UV in various wavelengths for interest in small growth chambers.

"All true science trusts nature until it is proven to be wrong, not the other way around. " Working in science industry for decades I don't think that is really true, but hey that's ok.

I know you think MH is the best light for coral, but not everyone agrees with you! Yes I am familiar with your 80 or 90% rule that nothing can hit that last 10% but I think it's mostly observational bias.

And JDA, you are in my top 10 most respected reefers just FYI. We don't have to agree on everything!