lightning 101

[Mihai]

I think I pretty much read lots of theory about lightning for reef aquariums.

My problem is with the practical aspects: there are different types of lights (NO/HO/VHO/PC/MH), and in each different types of lamps (XM/Iwasaki/???/???) each working with lots of different balasts (electonic/tar x MV balasts or standard balasts). Some combinations work better than others...

Furthermore, they cost significantly different, consume different powers, should be replaced at different time periods.

That's a MESS.

Did anybody put at least some of this information together somewhere (I checked the library, it's not there)? Digging it out of the message boards doesn't seem the right thing to do. This info is also not available in any of my books (M. Paletta - New Marine Aquarist, Fennner - Conscientious, Delbek & Sprung, Fenner & Calfo Reef Invertebrates, Nilssen + Fossa - reefs secrets). Also reading the ads on the package of the bulbs (online at marinedepot or hellolights) doesn't seem very reliable either...

So, can I find this type of info anywhere?
Thanks,
Mihai

Last thing: why do people supplement their 10000K lights with actinics? Do you get the same effect with 13000K?

 

[tangir1]

>...That's a MESS.
Yeah, I know....

as for your last question, the only reason for supplement is to enhance the appearance of the tank to the viewer. Supplementing is more flexible due to the different combination you can have, while there is only a limited selection of bulb, and you don't have much control from one bulb to another other (QA is a very tough issue with HID bulb), and from the same bulb at one time to another.

 

[Mihai]

Besides there are SE vs DE bulbs. It seems that DE produce more light per watt.

Really, nobody put this kind of info together?
Thanks,
Mihai

 

[Anonymous]

The closest to that info is Sanjay Joshi's testing data, but that isn't even comprehensive. The problem is there are always new bulbs and ballasts entering the market, so it is really hard to tell what works best - and the word best means different things to different people.

The best thing to do is start a thread like this and ask what people are using and then take a look at some pics of their tanks.

Here is what I think in a nutshell:
MH is the way to go. You get glitter lines and you can grow whatever you want.
I like the 250 watt DE bulbs because they are damn bright, seem to use less electricity and you get a wide choice of bulb temps. I also like that they usually come in pendants, so no muss or fuss with reflectors or wiring.
I use a combination of 10 K and 14 K bulbs, and I suppliment with actinic VHO. See my next post for more on why the combinations.

 

[Anonymous]

as for your last question, the only reason for supplement is to enhance the appearance of the tank to the viewer.

There may be more to it than that. I recently went to a talk by Steve Tyree, the same on he will be giving and MACNA, where he talked about the different spectrums of bulbs, different light requirements of coral, and reasons why different corals are different colors under different lights.

IIRC, the spikes in the curve of the pigments that allow the coral to photosynthesize have a couple of spikes. A 65K and a 10K bulb cover roughly the same spike, while 20K and actinics roughly to cover the other - although they cover the spikes differently. The idea is to cover those spikes as completely as possible - so you combine the bulbs that allow you to do that.

 

[DaisyPolyp]

A 65K and a 10K bulb cover roughly the same spike, while 20K and actinics roughly to cover the other

That statement is slightly misleading... A lot of good studies have come out recently on the effects of different wavelengths of light on corals. The short answer is that you want to aim for light in the 440-480nm range (blue). There are 2 spikes of photosynthetic activity for corals: 440-480nm and ~660nm. BUT, these spikes are not anywhere close to being equal. At 460nm most corals have an absorbance rate of 1.3 whereas at 660nm the absorbance rate is 0.2 if present at all.

What does all this mean to you? well, if you use the right spectrum of lighting, you don't need near the amount of wattage that you would at 10,000K. and that means more money in your pocket.

Most people try to mimic sunlight by using a lot of 10K and 6,500K lights. Most of that spectrum never reaches the coral either because the water filters out the longer wavelengths, or because the coral pigment reflects light of that frequency. So they must use a lot of wattage to get the small amount of blue light produced by that temperature of bulb.

...and one more thing while i'm rambling on:
It has been observed that anything in excess of 200watts of 440-480nm light, is not used by the corals, they actually slow down their systems in response to the extra light. (the exception to this lighting rule are clams)

 

[Anonymous]

You really want to understand lighting you need to take some upper physics classes.

 

[Mihai]

You really want to understand lighting you need to take some upper physics classes.

I did! It is the particle wave dualism that stands in the way of picking my ballasts .

Indeed, it seems reasonable that I'll go with 250 DE halides. There are many things that I do not understand though (and I'd like to understand before I spit out cash). For example, is the DE bulbs life shorter/longer/equal to SE bulbs life? What's that a poendant, and how is it different from a reflector? Do they require special balasts? Do they run hotter than SE? etc.etc.etc.

See my point here?
Thanks,
Mihai

 

[ChrisRD]

is the DE bulbs life shorter/longer/equal to SE bulbs life?

I don't know that there's been any comparison studies to test this, but the DE lamps I have used seem to have at least a similar lifespan to what people are getting out of comparable SE lamps. I don't think there's a big difference, but the DE lamps may last a bit longer. Halide lamp life (SE or DE) is highly variable depending on what particular model of lamp you're using and what ballasts you're running them on. They can be useful for as little as 6 months in the worst cases, and several years in the better cases...

What's that a poendant, and how is it different from a reflector?

A pendent is just the small hanging fixture that holds the lamp. The reflector is the actual polished aluminum behind the lamp. You always see DE lamps come in a pendent fixture because they don't have an outer glass envelope around them like an SE lamp so they require a UV shield (which is mounted in the pendent).

Do they require special balasts?

Yes, DE lamps require what is referred to in the hobby as an "HQI" ballast (although the term is used incorrectly). Some SE lamps can also be run on these ballasts, but it doesn't work the other way around (ie. you can't run a DE lamp on "regular" halide ballasts).

Do they run hotter than SE? etc.etc.etc.

Tough question to answer because the ballast will play a big role in how hot a lamp/fixture runs. Comparing an SE and DE lamp of similar wattage, color temp., etc. running on similiar ballasts I don't think there's much of a difference.

One difference between the two lamp types that could give the impression that DEs run hotter is that DE fixtures generally have no fans and just rely on ventilation (convection cooling). Many SE fixtures have cooling fans built-in. Because DE lamps lack the outer glass envelope like SEs have, it's generally advised that you don't point a fan directly at them as the cooling effect on the lamp can interfere with it's operation. For this reason you generally don't see fans in DE fixtures and as a result these fixtures run hotter to the touch, so people may get the impression that the lamp itself is running hotter (which may not be the case). The short, short version - if you can manage heat with SE halides, you can manage it with DEs as well.

HTH

 

[Mihai]

Chris, thanks for taking the time: you're a gold mine. I assume that 3-5 years from now I'll know these things too, I just doubt that my tank can wait that much.

In the light of what DaisyPolyp said, do I get it right that the white light (10,000K) is mostly for my eyes, while the actinic suplements are for the corals? This does not seem to be the prevailing wisdom though... any references/links/experiences with this?

It was my impresison (from some curves that I saw on the internet) that the saturation point at most corals is way higher than the compensation point (if compensation is reached with, say 200W of MH saturation would be somewhere at 1000W - 2000W).

Once more, I reiterate my main question: it seems that the information that Chris just provided is not available anywhere on the Internet. Is that right? That would be a pitty, as Chris will have to spend the time with the next noob that comes at RDO.

Mihai

 

[DaisyPolyp]

Mihai, you are correct, most of this information is not readily available. Maybe the admins should "Sticky" this thread.

You are correct in assuming that the 10,000K is for display of your tank, not as efficient for photosynthesis as 20,000K. The saturation point for most stony corals is ~200watts of 440-480nm light, or approx 350µMOL.

This information is available in 2 seperate studies:

"In situ underwater measurements of photosynthetic activity of coral zooxanthellae and other reef-dwelling dinoflagellate endosymbionts" by P.J. Ralph et. al, Department of Environmental Sciences University of Technology, Sydney. Published in "Marine Ecology Progress Series" Vol. 180:139-147, 1999

"Photobehavior of stony corals: responses to light spectra and intensity" by O.Levy, Z. Dubinsky, and Y. Achituv, Faculty of Life Sciences Bar-Ilan University, Israel. Published in "The Journal of Experimental Biology" 206, 4041-4049, 2003.

 

[ChrisRD]

You are correct in assuming that the 10,000K is for display of your tank, not as efficient for photosynthesis as 20,000K. The saturation point for most stony corals is ~200watts of 440-480nm light, or approx 350µMOL.

For those of us not familiar with these studies, would you mind quoting the portion of the study where these statements appear?

 

[ChrisRD]

In the light of what DaisyPolyp said, do I get it right that the white light (10,000K) is mostly for my eyes, while the actinic suplements are for the corals?

I think many experienced hobbyist would say just the opposite. The whiter lamps tend to produce higher PAR levels than the bluer lamps in similar wattages. Many experienced reefkeepers report greater coral growth rates under 6500K and 10000K lamps with slower growth rates under 20000K lamps. Many report nicer coloration under 20000K lamps. Of course this is mostly anecdotal because there are lots and lots of variables involved...

IMO, it's a fairly complex issue because there's a lot more to it than chorophyll absorption curves (ie. showing that blue light is most useful for photosynthesis). Corals also harvest and alter other light wavelengths using a variety of absorbing, reflecting and flourescing pigments. Most photosynthetic corals are highly individual and adaptable and it's pretty much impossible for anyone to quantify exactly what is "best" for any given coral.

Probably the closest thing to ideal is what Righty referred to above (based on Steve Tyree's work) - using high intensity lighting that covers several key spectrums...

 

[Mihai]

Daisy,

Thanks for the references; when you refer to 200W of 440-480nm, do you mean over a tank how big? 48"? 24"? I also see that you say that this is good up to 5 m. This is probably not correct for tanks:
if my understanding is correct in tanks the light goes down with the square of the distance. So if you have some intensity 20cm below the surface you'll have 1/25 of that intensity at 1 m and 1/625 at 5m...
(it's true that under the sun things are about the same between 1-5m but not in our tanks...).

Mihai

 

[DaisyPolyp]

when you refer to 200W of 440-480nm, do you mean over a tank how big? 48"? 24"?

This is the amount of energy that should be present on the surface of the coral. The placement of the actual light depends on structure of bulb, angle of reflector, etc.

I also see that you say that this is good up to 5 m. This is probably not correct for tanks:
if my understanding is correct in tanks the light goes down with the square of the distance. So if you have some intensity 20cm below the surface you'll have 1/25 of that intensity at 1 m and 1/625 at 5m...
(it's true that under the sun things are about the same between 1-5m but not in our tanks...).

This is partially true. Remember though, that different wavelengths of light have much different absorbtion rates in water. More specificly, light in the range of ~460nm is very blue and passes through water fairly effeciently (this is probably why coral has evolved to target these wavelengths). The research conducted thus far shows several marine "levels" of light absorbtion and photosynthetic activities. For marine aquariusts, our needs do not extend past the 5m level (unless there are some REALLY big tanks out there).

The whiter lamps tend to produce higher PAR levels than the bluer lamps in similar wattages.

This also is true. The 2 main factors here are that water very rapidly absorbs most of the wavelengths of white light, and also coral pigmentation tends to reflect most of the white light spectrum.

For those of us not familiar with these studies, would you mind quoting the portion of the study where these statements appear?

Absolutely.
From O. Levy's study:
The light environment is an important component of the
productivity, physiology and ecology of corals (Dustan, 1982;
Dubinsky et al., 1984; Porter et al., 1984; Falkowski et al.,
1990). Underwater light decreases exponentially with depth,
roughly following the Beer–Lambert law. Underwater light is
attenuated by the water itself, by dissolved and suspended
matter and, most importantly, by phytoplankton. Light
attenuation is not uniform over all wavelengths, and the water
column behaves like a monochromator, narrowing the
spectrum of the most penetrating light to a relatively narrow
waveband (Falkowski et al., 1990). In the clear oligotrophic
waters surrounding reefs, light extinction in the violet and blue
parts of the spectrum is minimal, while its attenuation is higher
at longer wavelengths.

chlorophyll was extracted in 90% acetone, the
absorbance spectrum at 400–700·nm was measured using a
Cary spectrophotometer (Varian, Palo Alto, CA, USA) and the
concentration calculated using the equations of Jeffrey and
Humphrey (1975).
The homogenate was centrifuged twice in
seawater, at 1500·g for 15·min in order to separate the algae
from the host tissue. The zooxanthellae pellet was taken
for pigment identification by high-performance liquid
chromatography (HPLC), using the reverse-phase HPLC
system after Yacobi et al. (1996). Pigments were identified
using ChromaScope (BarSpec, Israel), a spectral peak analyzer.
The pigments were identified by the spectral data of the peaks
separated by HPLC and their retention times, using the data of
Rowan (1989) and Jeffrey et al. (1997).
A fast repetition rate fluorometer (FRRF) was positioned on
a tripod adjacent to the flow tank. FRRF measurements were
taken by aiming the instrument at a coral in the tank and
triggering the instrument. Measurements were made in the dark
on corals with expanded and contracted tentacles. The action
spectrum for photosynthesis was obtained by FRRF taken with
corals illuminated by wavelengths of 400–700·nm. An
illumination intensity of 10·mmol·quanta·m–2·s–1 was obtained
using the Xenon lamp and monochromator.
The FRRF technique
enables non-invasive and rapid measurement of maximum
quantum yield of photochemistry in PSII (Fv/Fm, where Fv is
variable fluorescence and Fm is maximum fluorescence) and
the photosynthetic parameter Sigma, which is the cross section
of PSII (sPSII) (Kolber et al., 1998).
The spectral data of the separated peaks
revealed that most of the major pigments have considerable
absorbance between 400–540·nm, with major peaks between
440–480·nm. The widest absorbancy spectral profiles belong
to the accessory carotenoid pigments, such as perdinin,
diatoxanthin and diadinoxanthin, which display blue/
blue–green absorption bands that partially overlap the
chlorophyll absorption bands in that domain (Fig.·4).

 

[DaisyPolyp]

continuing with P.J. Ralph's study:

We found that three species of coral (Acropora aspera, Goniastrea sp. and Porites sp.) which grow in the shallow lagoon of Heron Island, all displayed an apparent mid-day down-regulation. The above figure shows the change in electron transport rate in Acropora aspera as related to changes in diurnal light. The decline in photosynthetic activity corresponded with the period of highest light. During the afternoon the photosynthetic activity recovered, this implies that this was a regulatory response, not damage from the high light.

 

[DaisyPolyp]

Continuing with P.J. Ralph's study:

This graph shows the photosynthetic rate for Acropora in 3 different levels of water depth with the same light source.

 

[DaisyPolyp]

Now obviously there is a lot more information contained in these studies, and I would be happy to send them to anyone who is interested.

 

[Mihai]

I see what you mean. As I suspected, the studies refer to sunlight.
Sunlight intensity decreases in water differently depending on the wavelength (due to absorbtion as noted).

In our tanks absorbtion does not play a major role unless you have dirty water (yellow pigment or lots of floating stuff).

In our tanks a different mechanism results in a change in the distance to the bulb (as I said, changes with the square to the distance).

Hence I might have in my tank the same intensity at the surface as the surface of the ocean , then at 10cm the same intensity as the ocean at 5 m, then at 20cm the same intensity as the ocean at 12m, etc.

Also, I don't think that measuring light energy available at some coral and making it equal to the electrical energy needed to power a bulb is quite right: for one, the efficiency of the bulgs is not 100%. Second much of the light from be bulb is lost (gets out of the tank).

M.

 

[DaisyPolyp]

Very good points. unfortunately there has not been very much research done that relates directly to our tanks, so as you said we may experience much different conditions. Perhaps the best bet currently is to do as righty said and just find out what is working best for reefers who have een doing this for a while. It's fun to be on the cutting edge, I think thats one of the best aspects of this hobby.