Lighting; PAR, Intensity, Spectrum?

[kadaytar]

Hi everyone,
I am new to this forum and my question is about lighting. As we all know lighting is one of the most complicated isues of reef keeping and also one of the most expensive equipments. I have read many articles about lighting but there are still many things that i am confused about.

These are my conclusions from my readings:
-Lighting is important at the point of photosynthesis and there isn't a big difference in the ratings of photosynthesis of the corals under different spectrums -4000K-20000K- if light intensity is the same. I think a
spectrum under 5600K may cause algae growth. At this point intensity is more important than spectrum for coral growth and coloration.
- PAR is the other important character of light for photosynthesis as well as light intensity.
- The bulbs having lower Kelvin temperatures have higher PAR values and provide higher light intensity than the ones having higher K degrees.
For example: 250 Watt 6500K IWASAKI has a PAR rating of 705 while 250W 10000K USHIO has 495 and XM 250W 20000K has 247. I found these comparisons at this page.

http://metricksystem.com/chris/250wcolour/

- -If photosynthetical zooxanthellea provides %30-40 of the coral's nutrition -depending on the species- light musn't be the only factor affecting the coral growth and coloration. IMO feeding and water current are the other important factors. Because if we dont feed our corals we will not provide them the rest of their nutritional needs. This will cause lower coral growth and the overgrowth of brownish zooxanthellea so the more brownish look of the corals.

- Fluorescent bulbs provide a more uniform ilumination than MH bulbs but since the MH bulbs are point source they are more intense and provide a better light penetration than fluorescent bulbs within a span of 2 feet.

- I am not pretty sure about this but generaly 48" fluorescent bulbs have higher lumen/Watt values than the smaller sizes of the same type.

Here are my questions:

- Can we say that light intensity affects the penetration of the light and PAR affects the rating of photosynthesis?

- If a high quality 6500K MH bulb has PAR and intensity ratings twice as much as a 20000K MH bulb having the same wattage can we say roughly one 6500K MH bulb provides the intensity and PAR values provided by 2x 20000K MH bulbs having the same wattage and can we go with one 6500K bulb instead of two 20000K bulbs if it provides the necessary PAR and intensity values?

- Since it is nearly impossible to find the Photosynthetic Photon Flux Density ratings of the bulbs can we simply use lumen/Watt ratings of the bulbs for having a general idea of light intensity of the bulbs? Is there any conversion formula for lumen/Watt to PPFD or any source showing the light intensity of different depths of tropical seas?

I have seen a Canadian made 40W 6500K fluorescent bulb having a light intensity of 3200 lumens i know that there some 4 footers having 3500 lumens. Roughly many of the 10000K 175 MH bulbs have a light intensity around 7000 lumens. Whenever we use 2x 4 footers having 3500 lumens we can get the same light intensity provided by a 175 W 10000K MH bulb. Yes MH's are more intense within 2 ' but we can use 3 or 4 40W fluorescent bulbs if we have enough space over the tank or we can keep the high light loving corals close to the surface. Kelvin temperature of the natural Sun light is around 5600K and many of the SPS corals especialy acroporas live close to the surface and the color temperature of the natural light musnt be so high in the shallow waters. So what makes 10K MH's superior than 6500K 40W fluorescent bulbs if we dont mind the color of light and dont have a space limitation in the hood?

- Isn't it possible too keep SPS corals under fluorescent bulbs if we keep them close to the surface, provide them enough light intensity, provide them enough water current, and feed them regularly with phytoplanktoon and zooplankton?


I know i have asked too many questions i hope my questions won't bother you.

Thanks
Kadir

 

[Len]

Hey Kadir, I moved this thread to the General Reef Discussion. The AAOLM forums are intended for discussion about articles written in Advanced Aquarist You'll get more views/responses in the GRD.

 

[kim]

First, you have a very good understanding of the issues. You don't know all of the solutions. Nor do I.

- Can we say that light intensity affects the penetration of the light and PAR affects the rating of photosynthesis?

No, intensity doesn't (in my mind) affect penetration. If you start off with more or less intensity, this will be directly reflected in the illumination in your tank at all levels. Twice as bright at the top....twice as bright at the bottom. Key is that in order to achieve adequate brightness at the bottom of the tank, you will need a certain minimum starting level.

PAR (which is a measure of light falling in wavelength 400 - 700 nm) is a measure of intensity. It is closely related to photosynthesis, but it isn't the whole story....not all those wavelengths are useful. So a high PAR lamp could be useless ! But it's a good guide.

If a high quality 6500K MH bulb has PAR and intensity ratings twice as much as a 20000K MH bulb having the same wattage can we say roughly one 6500K MH bulb provides the intensity and PAR values provided by 2x 20000K MH bulbs having the same wattage and can we go with one 6500K bulb instead of two 20000K bulbs if it provides the necessary PAR and intensity values?

OMG ! Depends what you want. And depends on the lamps. Just because a lamp has twice as much PAR as another doesn't mean that it is twice as good for photosynthesis. Also, the colour temperature of a metal halide is, at most, a crude indication of output (see AA this month....there are a lot of ways to create, for example, a 20,000 K lamp, and each is quite different).

Also, bear in mind that PAR stimulates growth, whereas a higher colour temperature lamp may, may, stimulate colouration. Do you want corals to grow rapidly or look nice ?

Since it is nearly impossible to find the Photosynthetic Photon Flux Density ratings of the bulbs can we simply use lumen/Watt ratings of the bulbs for having a general idea of light intensity of the bulbs? Is there any conversion formula for lumen/Watt to PPFD or any source showing the light intensity of different depths of tropical seas?

In order to convert, you need to know the precise spectrum. If it is daylight, driven by Sun, about 40 lumens corresponds to 1 PAR. But it would be reckless to apply this to halide lamps.

I have seen a Canadian made 40W 6500K fluorescent bulb having a light intensity of 3200 lumens

Yes, expect about 80 lumens/watt at this colour temperature (both halides and flourescents). Since surface intensity in the tropics is 80,000 lumens/m2 at midday, you end up with 1,000 watts per m2 of tank. This is where flouros trip up....they are fine, but you can't squeeze enough of them in if you want to replicate these conditions.

i know that there some 4 footers having 3500 lumens. Roughly many of the 10000K 175 MH bulbs have a light intensity around 7000 lumens.

The lumen reflects the human eye's response to light. One reason that the higher temperature lamps produce so few lumens is that the human eye responds well to yellow, less so to blue (and reds). So they appear less bright. The lower lumens is an indication of what this lamp looks like to you. That may be important, to you. Or not.

Kelvin temperature of the natural Sun light is around 5600K and many of the SPS corals especialy acroporas live close to the surface and the color temperature of the natural light musnt be so high in the shallow waters.

Correct, but add in the blue sky and daylight is more 6,500 K.

Isn't it possible too keep SPS corals under fluorescent bulbs if we keep them close to the surface, provide them enough light intensity, provide them enough water current, and feed them regularly with phytoplanktoon and zooplankton?

Your problem may be (a) total light output.....how many fluorescent lamps can you include plus (b) intensity....the halide gives very intense patches of light (plus some shadows, of course).

kim

 

[kadaytar]

Thanks Len for moving the thread i thought that i couldnt get any answer and thanks alot Kim for taking your time and answer

As far as i know PAR is the only usefull part of light for photosynthesis- radiation in 400nm-700nm waveband. The other wavelenghts have no influence on photosynthesis of corals. The intensity measure we should look for is Photosyntetic Photon Flux Density. PPFD is the incident photon flux density of PAR, the number of photons (0.4-0.7 µm) incident per unit time on a unit surface. But i havent seen any info on any bulb regarding PPFD If these are true we cant say that high PAR bulbs may be useless unless they have insufficent PPFD values. IMO the more PAR means the better growth. But unfortunately we cant even get closer to the PAR values in the nature even with the MHs

At the point of coloration, color of organisms may be missleading and cant be considered as a sign of health. Because all the corals have reflective pigments on, they may show different coloration depending on the color of light but this doesnt show the real color of the corals. If we use only 6500K bulbs corals may have a pale color but i believe that it can compensated by using intense actinic 03 bulbs. I used to have a 55G with 4x 110Watt VHOs. 2x10000K 2xactinic 03. I bought a purple acro and purple tip montipora digitata-brown stalks with purple tips- frags from another hobyist keeping them in a 70 G tank under 2x 250 Watt Radiums and NO actinic fluorescent bulbs. Whenever i told him that i had VHO bulbs he told me that i couldnt get the same coloration - sure i was pissed off - Yes i couldnt get the same coloration that purple tip monti didnt have brownish stalks in my tank its whole body was pinkish purple. Purple acro frag had had a whitish purple on the body and pale purple polyps in his tank and same thing happened with that acro i couldn get the same color it was as purple as an egg plant in my tank under VHOs. I placed them 6" down from the water surface right between the actinic and 10K bulbs. I ran a power head close to the surface and a filter media removed HOB filter to be able to create a good surface water movement. I believe that the ripple effect created by MHs affects the light penetration. Whenever i put them under only 2x 10K bulbs or only 2x actinic bulbs they got brownish.

Yes i believe that surface intensity is too high in the tropics but the depth of the tank i want to keep is only 18". %90 of the light is attenuated up to 15 meters depth in the nature. The light intensity in the areas where the moderate light loving corals live is around 10000lumens/m2 - i am not sure about the exact amount but very close to 10000. If we think that the dimensions of the tank i am planning to keep SPS under fluorescent bulbs are 120cm l x32cm wx 45cm h we will see the surface is only 0.38m2 so i think 4x40Watt 3500 lumens bulbs may create the same intensity and upper levels may have enough intensity for SPS, am i wrong :?:

Here is a link to Scott Morell's 120 G SPS tank under 7x40W NO bulbs

http://www.garf.org/ScottNewLook/OldLookFront640.JPG

This is another SPS dominated tank under T5 HO fluorescent bulbs

http://www.sgreefclub.com/srctotm/srctotmdanano.htm

I dont want to be missunderstood i am not trying to say that fluorescent bulbs are equal to MHs. Sure thing they put more light and they have a better penetration ability but i still believe- at least i wanna believe- that it is possible to keep healthy colorfull SPS corals under fluorescent bulbs whenever we pay attention some little points such as going with long- shallower tanks, keeping the light loving corals close to the surface, surface water movement, intense actinic 03 support, appropriate rock scaping and coral placement, feeding etc.

Kadir

 

[kim]

Kadir,

The trouble with PAR is that chlorophyll doesn't simple utilise 400 - 700 nm wavelengths. Depending on the type, it is quite specific as to which bits it uses. So PAR is an indicator, nothing more.

If halides emitted a continuous spectrum, this wouldn't be a problem....but they do not. They themselves concentrate their emission at certain wavelengths. If those miss the targets of chlorophyll......

Just to muddy the water, it seems that corals have pigments to convert light to the wavelengths needed by their zooxanthellae. So maybe it doesn't matter !

If you plough thru' some past issues of Advanced Aquarist you will find PAR data for lamps.

Anyway, I'd suggest that you follow your nose. There is little certainty here....you've clearly done your research, formed some opinions, you have a plan !

Best of luck, but I don't think that you are relying upon that,

kim

ps Do you have a link any data for the output of 03 Actinics btw ?

 

[reefann]

ps Do you have a link any data for the output of 03 Actinics btw ?

I to would be interested to see that if you have a link.
_________________
chocolate chunk photos

 

[kadaytar]

I dont know if this link works for you guys , this is the only one i know. Actualy it is not about the output of actinics but there is some usefull info.

www.wetwebmedia.com/../marine/setup/lig ... icfaqs.htm

Yes Kim, you are right about PAR. I missed that important point. PAR is the waveband between 400nm - 700nm but chlorophyll may not utilize all the wavebands at the same amount and a bulb radiates within this waveband may not hit the target as expected, did i get it right? At this point is it true to say high PAR or low PAR. PAR is PAR . What is high PAR? As far as i can understand it is not an intensity or power measure. Also i think there is dilemma about PAR. Because these are the colors between 400-700nm
380 - 436 nm purple
436 - 495 nm blue
495 - 566 nm green
566 - 589 nm yelow
589 - 627 nm orange
627 - 780 nm red

We know that zooxanthellea doesnt utilize red light but it is within the waveband of PAR. May this PAR thingy work for plant's chlorophyll? Does the chlorphyll on zooxanthellea utilize the same waveband with the plants?

Kim, actualy i am not planning to use NO bulbs i am gonna go with
1(maybe 2)x175W 65KK and 2x95W blue VHO's over a 35 gallon
But there is something pisses me off. When a hobyist on a limited budget asks if he/she can keep SPS corals under NO, PC or VHO fluorescent bulbs the answer is NOOOOOOOO :evil: :!: :!: . You gotta go with MH. Why???? Because the other reefers say sooooo. MH's are the way to go. What is your scientific base? Have you made any search? Do you know anything about the outputs of flo's. Hmmm nooo but you cant keeep SPS under flo bulbs.
I am not saying that we can keep a 24" or higher SPS dominated tank under Flo lighting. What i want to say (or want to learn more about) is that if we pay attention some points we can keep SPS corals under flo lighting at the upper levels of shallower tanks. There are some reefers succesfully keeping SPS corals under flo bulbs so why can't the others ? But sure there are some critical points and i would be glad to learn if there are some other reefers knowing different tricks and share them

Kadir

 

[Unarce]

We know that zooxanthellea doesnt utilize red light but it is within the waveband of PAR.

For the newbies out there, the wavelengths in the red spectrum are the second most important for photosynthesis and are utilized by zooxanthellae. :wink:

kadaytar,

You should check out this thread for some really good reading. This reminds me, I've got to BUMP it.

http://reefs.org/phpBB2/viewtopic.php?t ... highlight=

 

[kadaytar]

So what does this mean? I think i still have a missunderstanding.

It is important to note that photosynthesis-quenching pigments (such as diatoxanthin) do not absorb red wavelengths - dynamic photoinhibition involves only absorption and dissipation of short-wave radiation such as violet and blue bandwidths. A water column rapidly attenuates red wavelengths (something on the order of 40% in the first meter of the most optically transparent seawater, Jerlov Oceanic Type 1 - 1976) so many corals would not need a specialized pigment to divert red light energy away from photosystem reaction centers. If we disregard the possibility of red-reflective or red-absorbing (fluorescent) pigments acting as photoprotectants, then zooxanthellae/corals do not possess a pigment to protect them from photo-reactive red light energy. It seems the mechanism they possess is a reduction of zooxanthellae and/or photopigment content, possibly leading to total bleaching. Results from recent experiments suggest that degrees of pigment reduction/bleaching are related to red light intensity of artificial light (Riddle - in press).

Evidence does not discredit the notion that red light - at lower intensity - is a factor regulating zooxanthellae pigment content, that is, zooxanthellae might adjust pigment content until equilibrium between PS II and PS I is obtained. If the red light intensity is great enough, photoacclimation may not be possible, and bleaching is a last ditch effort for survival.

link to the whole article
http://advancedaquarist.com/issues/june2004/feature.htm