UVA LED's...what do they do?

[thewackyreefer]

So I'm looking into the Sunbrite LED system (info here) and I noticed they have a UVA LED bulb for SPS. What exactly is the point of the UVA lighting and how would this differ from a a normal LED?

 

[swannyson7]

I was wondering the same thing the other day when you posted the thread about these fixtures. The LED fixtures I bought from Luke have 4 UV spectrum diodes, but I'm unsure of their purpose. I always thought that UV light would damage corals. I remember on RC someone once asked about using a blacklight instead of actinincs and someone gave a long-winded scientific reason about how the UV wavelength would damage tissue. I'll see if I can dig up a link for it.

 

[reeftank21]

I think they are referring the wavelength maybe in the 420nm range. I've heard the same about how UV may cause damage to corals and don't understand. The UV lights that I've seen are a much more purple or violet color. I've used UV flashlights to look at corals and it does reflect some other colors that the 460nm range does not. The light that I have used are use more for automotive use and dye testing on A/C systems.

 

[thewackyreefer]

Interesting, I didn't realize those 4 diode's in the fixtures I have from Luke are UV as well. I'm taking a trip to check out one of the fixtures tonight so I may be able to get some more info.

 

[acrotrdco]

UV-A is 315nm - 400nm, so the typical 405nm LED bulbs you found on your fixtures, aren't exactly UV-A. It's close to UV-A but not quite, I'd just call it violet, real UV-A light is not visible to the human eyes, but the violet bulbs you saw in your LED fixtures should be giving off very dim violet light since it still have some blue spectrum in it.

I've yet to find any real 420nm LED bulb, most that advertise they're 420nm are usually just 405nm or lower, because there're more applications that need LED bulbs of those spectrums (legal tender watermark checker, black-light T5 replacement, etc.), however 420nm is mostly used in photosynthesis applications only such as plant growing and used in our reef aquariums.

 

[swannyson7]

UV-A is 315nm - 400nm, so the typical 405nm LED bulbs you found on your fixtures, aren't exactly UV-A. It's close to UV-A but not quite, I'd just call it violet, real UV-A light is not visible to the human eyes, but the violet bulbs you saw in your LED fixtures should be giving off very dim violet light since it still have some blue spectrum in it.

I've yet to find any real 420nm LED bulb, most that advertise they're 420nm are usually just 405nm or lower, because there're more applications that need LED bulbs of those spectrums (legal tender watermark checker, black-light T5 replacement, etc.), however 420nm is mostly used in photosynthesis applications only such as plant growing and used in our reef aquariums.

You're correct, the UV lights do emit a very faint violet light. Have you heard anything about this spectrum damaging coral tissue?

 

[acrotrdco]

You're correct, the UV lights do emit a very faint violet light. Have you heard anything about this spectrum damaging coral tissue?

Not at all, in fact, if you look at the following spectrum from the popular T5 tubes, you'll notice they ALL have 420nm - it's vital to the success of T5, according to the Germans, 420nm is an important wavelength needed for corals to improve coloration.

Giesemann Aquablue Plus

ATI Aquablue Special

Giesemann Actinic Plus

ATI Blue Plus

 

[Hahnmeister]

UV-A: not really dangerous
UV-B:can be dangerous in large amounts, otherwise for tanning and skin cancer as well as vitamin-D production
UV-C: kills everything

If you look back into the research Dana Riddle did about the many types of photosynthetic spectrums that corals can use (since its much more complex than your typical plant), you will see that some actually have an activation in the UV-A spectrum.

I have not found more than one or two 420nm LED's. 405's are pretty common (blacklight looking), but I have also found a good deal of 410nm ones in the 700mA current range. Their output is something like half of what the royal blues are though, so they look very dim, and with RB's and Cyans being so bright, LED makers so far have been leaving out the true actinic.

It is also speculated that UV-A is what is needed for the long term health of some clams. UV-B is speculated to be important for the health of croceas (which can be in very shallow waters or even exposed to air for hours each day under the beating sun). I dont know myself.