Can A Blacklight Stimulate Growth?

[H2oH2o]

I had an idea of retrofitting a 24" blacklight to my reef tank to go along with my moonlights and to give it a cool apperance.

Is this good for coral growth or will it harm them?

[Blown 346]

No, a black light wont help with growth. It also wont harm anything.

[daytonians]

I dissagree. Although blacklights give off UV light that is near the visible spectrum which is not as bad as UV with longer wave lengths, all UV light is damaging to both corals and people's eyes. I would not use one for any extended length of time. There are cool to turn on for short periods to show people the colors, but that's the most I would do. UV causes cataracts, so don't use them long if you like the ability to see.

[MCsaxmaster]

They do put out near-UV (long wavelength UV) which is not all that dangerous, as mentioned. They also don't put out a whole heck of a lot of it, especially once you get about a foot or more from the bulb (intensity declines as the square of the distance) so they probably don't put out enough UV to cause any real harm, though realistically without taking some measurments it's hard to say. Also, they're so dim they probably won't really do anything good for photosynthetic organisms either (too dim to 'register' with the photosynthetic aparati). It's fine to use them, but it may be best to run them intermittently, to be on the safe side (though honestly, the risk is really very minimal).

cj

[SE TX HYDROPONICS]

has anyone used them? I am curious as to how the tank looked with them in use....

[NirvanaFan]

I'd be very cautious about water getting on the hot light. I remember when I was a kid one blew up because water got on it. The person put their head in the water to bob for an apple. They got one and flung their head back quick and water flew off their hair and onto the light. It exploded instantly.

It could have been due to the very cold water, the bulb, or water in general. If I were you I'd be very cautious about putting that in the canopy, or even near the tank.

[daytonians]

To clear up a few things. Near UV is UV light with short wave lengths. Not long as stated above.

Being too weak to cause any damage is too broad a statement to make any sense. Like any type lighting, it depends how many watts you are using. I would not be too afraid of a 2 watt bulb, while a 200 watt bulb may be able to do serious damage fast.

In general, corals do not fluoresce any more under near UV than they do under 420 or 480 Actinics, and Actinics are totally safe for coral and human alike.

Why take a chance for no reason.

[tcmfish]

I use two on my 75 gallon and when i shut my metal halides off for a few days when the tank was just set up the coraline on my new live rock took off it made it grow like crazy. also i keep them on 24/7 now when the halides are on they have no effect but when they are on at night the green shows up very nice but they are so dim that you can barely see through the tank with them on. The tank has been set up since january and all the corals have been growing like crazy sps lps i have one soft toadstool that hasnt really grown but zoos sps lps everything is doing great. fish are fine all of them are healthy. I run two 250 10ks and 2 blacklights.

[pbukow]

Isn't the reason that some corals have such vibrant flourescent colors is to reflect some of the UV rays bulbs put out, so wouldn't that just make them more colorful to counteract the added UV of a blacklight if introduced the light to them slowly and over time?

Or am i just way off and don't know what i'm talking about?

[Paul B]

I used a black light continousely for about a year. I diden't notice any effects good or bad. It is not very noticeable and not at all with any other lights on. It looks a little eerie and interesting when no other lights are on..
Paul

[daytonians]

I think that UV light may increase coloration of corals if exposed everyday. The problem is, to be strong enough to make the corals color up, it would have to be strong enough light that it would be extremely dangerous to human eyes. It may also damage the corals more than increased coloration can protect. I am sure it would vary from species to species.

By the way, I know a guy that seriously damaged his eyes with UV light. He was mig welding without a mask. Doing spot welds on a car. He thought he would be safe just closing his eyes when he pushed the button to weld. He was wrong. UV can go right through your eye lids. Yes, that was way brighter than anything you would ever use in a tank, but it shows how dangerous it is to mess with UV light.

[MCsaxmaster]

To clear up a few things. Near UV is UV light with short wave lengths. Not long as stated above.

UV-A (aka long-wave UV) ranges from 400 - 320 nm, UV-B from 320 - 280 nm and UV-C from 280 - 200 nm. Technically all of this is 'near UV' with 'far UV' ranging from 200 - 1 nm. As such, what I should have said and what I meant is that blacklights produce UV mostly near the visible spectrum, that is, mostly UV-A which is not particularly dangerous. They produce very little UV-B (damaging) and essentially no UV-C (DEADLY). UV-A is long wavelength UV light, not short...

Being too weak to cause any damage is too broad a statement to make any sense.

I believe I said, "...they probably don't put out enough UV to cause any real harm, though realistically without taking some measurments it's hard to say." I did not say that UV-A cannot be damaging or that UV light in general cannot be damaging, but that a blacklight likely cannot produce enough UV light of any wavelength (especially considering that they produce mostly UV-A, which is not very damaging) to be a serious threat. You'll get more UV-A from the midday sun in 10 minutes than you will in 12 hrs a foot from a blacklight. Considering the very slow rate with which sea water aborbs UV as compared to other wavelengths of light, it is very likely that organisms on reefs get more UV than this even in deeper water (100 ft. +).

Like any type lighting, it depends how many watts you are using. I would not be too afraid of a 2 watt bulb, while a 200 watt bulb may be able to do serious damage fast.

Firstly, is not the discussion about blacklights? Have you every seen a 200 watt blacklight or onenthat focuses its light to the same area as a 2 watt bulb? And for that matter, the wattage the light takes is meaningless: only the amount of UV light matters. For example, I couldn't care less about standing in front of a bank of fluorescent bulbs that take 10,000 watts to run. I wouldn't want to stand in front of even a single 54 watt UV sterilizer bulb though.

Isn't the reason that some corals have such vibrant flourescent colors is to reflect some of the UV rays bulbs put out, so wouldn't that just make them more colorful to counteract the added UV of a blacklight if introduced the light to them slowly and over time?

No. Corals use compounds such as mycrosporine-like amino acids to absorb damaging UV-B. These do not emit fluorescense that we can see so they are, to our eyes, colorless pigments. Green fluorescent protein and all the GFP-like fluorescent and non-fluorescent proteins (all the ones that give corals their nice colors) absorb light in the visible spectrum or slightly into the UV-A. We still aren't sure what the function of these proteins might be (their function might have nothing to do with the fact that they absorb and fluoresce light, or then again it may) but whatever their function they have nothing to do with protecting corals from UV light. They don't absorb UV light that corals need protection from.

Chris

[daytonians]

Chris,

Your thinking is backward. UV near the visible light spectrum is UV with shorter wave lengths making it high frequency. The numbers you quote are for frequency, not length. UV-A is shorter wave length than UV-B. The shortest wave lengths are in the Infared area of the light spectrum.

No I have not seen a 200 watt black light bulb. I have seen people using 200 watts worth of bulbs in more than one fixture. You are no doubt not old enough to remember the 70s when Black Lights were all the rage.

[MCsaxmaster]

Matt,

I hate to say it, but you're mistaken. UV-A light has a wavelenth of 400-320 nm (nanometers). Frequency and wavelength are inversely related as described by f = c/lambda where f is frequency, c is the velocity of light and lambda is the wavelength. A wavelength of 400 nm gives a frequency of about 7.5 * 10^14 Hz. For UV-B light at 300 nm the frequency is about 1 * 10^15. IR radiation has a very low frequency and long wavelength compared to UV.

cj

[daytonians]

CJ,

You are probably correct. Frequecy charts usually go from left to right with higher values on the right. I wonder why light graphs are always made backward. Interesting.

[aninjaatemyshoe]

I seriously doubt a blacklight outputs enough UV to be a problem. Seriously, do you think those little lights output anywhere near what corals see in terms of UV light in the wild? Need a simple test: have someone stand by a black light for 3 hours and then have someone stand in direct sunlight for 3 hours. Who do you think is going to get the darker tan? Personal experience: I used to sleep next to blacklight and I never woke up with a sunburn.

[jest]

Hey I thought maybe some of you guys might find these interesting :

http://www.blacklight.com/items/chmhl-250



There is a wide range of HID blacklights available.

Don't really know what they would do to coral ??

[DouglasTiede]

I do know that black lights kill fish in fresh water tanks!!

[aninjaatemyshoe]

Where did you get that info from Douglas? I'd really like to see the source on that. After all, why in the world would a blacklight be approved for home use if it was so harmful? I'm kinda getting the feeling that this is the same sorta hogwash like the idea that sleeping next to a clock radio gives you brain cancer.

[liveforphysics]

To cause flourecence in something, you may only shift towards longer wavelengths. Going backwords would be a violation of mass and energy conservation due to shorter wavelegnths having more energy per photon than longer wavelegnths.

If you wish to cause pigments which flourece deep blue and purple (400-430nm) flourecence, you must stimulate them with light of signifigantly shorter wavelegnth. I use 4x40w T12 NO BLB bulbs over my SPS reef to provide this lighting. It causes flourecence which is impossible to get from actinics (the tank also has 4x54w T5 HO actinics over it for stimulating lower frequency pigments).

As far as "dim" being applied to BLBs, I think the word would be better suited towards certian biomechanisms which raise signal to noise ratio here. If you have a pair of 40w T12 NO bulbs running, one being BLB, one being high efficiency flourecent, you will note the surface temp of the BLB lamps is cooler. If both bulbs draw the same energy in, and one bulb stays cooler, that bulb is emmiting MORE light than the other. It just happens that our eyes only see it at around 0.00002% the intensity which we view different wavelegnths like 555nM green. BLB uses something called wood's glass to absorb all the accidentally created visible wavelegnths, and it is still a more efficient lights than standard flourecents. Keep in mind, all of our lighting aside from incan's and LED's are first creating UV light, then floureceing this light with phosphors on the outside of the glass to drop frequency enough to put them in the visible range.

For folks concerned about dangers associated with BLB tubes, please ensure that you and your corals are never exposed to sunlight.

I dont have the means to conclude if the corals in my reef draw any benifit from the BLB tubes, however, aesthetically I am much more pleased than with actinics alone, as they give me more than just your standard greens and pinks showing under actinics.

Best Wishes,
-Luke

[daytonians]

An eye doctor told me that the danger was because those lights don't put out much visible light. If you go out in the bright sun you put on sun glasses or squint, plus the iris closes way down on your eyes.

With black light, your eyes don't see the light, so they stay wide open letting the light do it's damage.

Just passing on what I was told.

[aninjaatemyshoe]

Thats believable. But you'd probably have to stare directly at the light for a good amount for it to leave permanent damage. Of course, its not recommended to look at any lightbulb for a prolonged period. Still, I doubt that this will kill a fish.

[GreshamH]

Originally posted by jest
Hey I thought maybe some of you guys might find these interesting :

http://www.blacklight.com/items/chmhl-250



There is a wide range of HID blacklights available.

Don't really know what they would do to coral ??

Those are used in black light projectors We used those all the time in theators and other productions. FWIW, the dangers associated with black lights and humans is really in the context of being in a dark room with black light being the sole light source. As per some regulation from an agency I can't recall (FTC?) we couldn't run BLB's as a sole light source. The same agency regulates the use of lasers at events as well.

[mr.wilson]

The benefits and dangers of UV light was a big debate 20 years ago, but I haven't heard much on the subject of late.

UVA & B has been proven to kill coraline algae. This often happens when water changes are done with MHL lighting on, and UV exposure is increased. Coraline algae also tends to grow faster with certain MHL bulbs (Phoenix from my experience) and all T5 lamps. This too is likely to be the result of lower UV production.

Anyone who has had the misfortune of having a mogul socketed (double glass UV shield) lamp break, knows that the harmful UVB emitted can kill corals and fish within a few hours, so there is such thing as too much.

The issue that rarely comes up is the UVA & UVB output of aquarium lighting. With vitamin D synthesis and calcium uptake being the chief benefits, it's a wonder that UV lighting in the range of 290-305 NM is accepted as being essential in the reptile hobby, but largely ignored by the marine hobby.

In addition to the synthesis of vitamin D and subsequent calcium uptake, UV light has antibacterial properties, and gives our corals the flourescence that we pay top dollar for.

UV light travels well through water, so why aren't we assuring that our corals get the same amount of UV in our captive systems?

[ATJ]

I'm not aware of any benefits of UV radiation to marine organisms. There may be some sterilisation benefits but that's going to be about it. UVR can't be used (directly) for photosynthesis as it is beyond the reach of photosynthetic pigments which have a limit of around 400 nm, but can extend down to 380 nm.

The dangers of UVR on marine organisms are quite well known with damage to photosynthetic structures by UVB probably being the worst. What is interesting, however, is the adaptations of corals to high amounts of UVR, for example intertidal corals that are exposed to full Sun for many hours at a time, something that would be extremely damaging to many humans.

Of the published data on coral fluorescent pigments, the vast majority have excitation peak wavelengths greater than 400 nm (i.e. in the visible range). The few pigments with excitation peaks below 400 nm are still above 380 nm.

Just because an organism is exposed to something in nature does not mean it requires that thing to survive or be healthy.

The bottom line is that a blacklight will not stimulate growth.