If You're Serious About Lighting, Know This

Discussion in 'Aquarium Lighting By Dana Riddle' started by Dana Riddle, Jun 29, 2017.

  1. Dana Riddle

    Dana Riddle Well-Known Member Staff Member R2R Supporter Build Thread Contributor Article Contributor Expert Contributor

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    Per @GoVols suggestion:

    Lighting for reef aquaria can be as simple or complex as you wish to make it. If you’re really serious about lighting, these are some of the terms you might want to be familiar with:

    Accessory Pigment: A photopigment that absorbs light and transfers it to chlorophyll a and hence reaction centers. Accessory pigments in zooxanthellae include chlorophyll c2, peridinin, beta-carotene and a few others.

    Chlorophyll: An organic compound with a magnesium cluster that is capable of absorbing light. There are a few chlorophylls. Zooxanthellae in corals contain chlorophylls a and c2 (not chlorophyll b!)

    Compensation Point: When light intensity is sufficient to produce enough oxygen to meet the respiratory needs of the organism. Compensation points of zooxanthellae are usually less than 50 microMol/m2/sec.

    DLI (Daily Light Integral): The total number of photons that promote photosynthesis falling upon an area of one square meter per second. If we think of PPFD as the number of raindrops falling upon 1 square meter per second, DLI would be the inches of rainfall per photoperiod.

    ETR (Electron Transport Rate):
    The rate of photosynthesis and is the flow of energy between Photosystem II and Photosystem I. Interruption of this flow can create destructive pressures that can destroy a zooxanthella cell. ETRs are measured using a PAM fluorometer.

    Nanometer: One billionth of a meter.

    PAM Fluorometer: Pulsed Amplitude Modulation Fluorometer or ‘photosynthesis meter.’

    PAR (Photosynthetically Active Radiation): The bandwidth of radiation that promotes photosynthesis. It is generally those wavelengths falling between 400 and 700 nanometers, although some ultraviolet-a wavelengths will make photosynthesis happen. It is reported in units of microMol photons per square meter per second (µmol·m2·sec.)

    PUR (Photosynthetically Usable Radiation): That portion of PAR that is highly usable in photosynthesis. PUR varies among organisms. Zooxanthellae can utilize some portions of green radiation (up to ~550nm) while green plnts can use it to a much lesser degree.

    Photoinhibition: The act of regulating photosynthesis under conditions of high light. There are two types of photoinhibition: Dynamic and Chronic. Dynamic Photoinhibition is reversible response to high light (involving the xanthophylls diadinoxanthin and diatoxanthin. Energy that could be used in photosynthesis converts diadinoxanthin (DD) to diatoxanthin (DT.) In darkness, DT reverts to DD. In case the DD/DT Cycle fails to provide adequate protection, photoinhibition can become chronic. This occurs when excess light energy damages the mechanisms of photosynthesis and energy that could be directed towards growth or reproduction is channeled to repair. Long-term chronic photoinhibition can be fatal.

    Photon: A discreet particle of light.

    Photoperiod: For our purposes, the number of hours the aquarium receives light, either natural and/or artificial.

    Photosynthesis: A complex reaction where light energy converts a carbon source (carbon dioxide or carbonates) into oxygen and simple sugar.

    PPFD (Photosynthetic Photon Flux Density): The number of photons that promote photosynthesis falling upon a surface area of one square meter per second.

    Reaction Centers:
    Where photosynthetic reactions occur.

    Saturation: Saturation occurs when increasing light intensity no longer increases the rate of photosynthesis. Zooxanthellae saturation generally occurs at a PAR value of 300 to 400.

    Wavelength: A measure of a wave from crest-to-crest (or trough-to-trough.) Light wavelengths are measured in nanometers.

    Xanthophylls: Literally ‘yellow leaf.’ Organic compounds that, for our purposes, protect zooxanthellae/coral host from excessive light by shunting light energy away from the photosynthesis process. In corals, these include diadinoxanthin and diatoxanthin. These absorb blue light.
     
    Last edited: Jul 2, 2017
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  2. Brew12

    Brew12 Electrical Gru R2R Supporter Reef Squad Leader Reef Squad R2R Excellence Award Build Thread Contributor Article Contributor Partner Member 2018

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    Dana,

    This is great! Can you make it a sticky so it doesn't get lost?
     
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  3. GoVols

    GoVols VFL R2R Supporter MTRCMember R2R Excellence Award Build Thread Contributor Article Contributor Partner Member 2018

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    +1... :)
     
  4. Donovan Joannes

    Donovan Joannes Valuable Member R2R Supporter R2R Excellence Award Rest In Peace Build Thread Contributor

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    Great information!
     
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  5. GoVols

    GoVols VFL R2R Supporter MTRCMember R2R Excellence Award Build Thread Contributor Article Contributor Partner Member 2018

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    Thank You. :)
     
  6. revhtree

    revhtree Owner Administrator Staff Member Team R2R R2R Supporter Photo of the Month Award R2R Excellence Award Build Thread Contributor Article Contributor Partner Member 2018

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    This is great info!
     
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  7. Idal sarduy

    Idal sarduy Member

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    Thanks!
     
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  8. Salty1962

    Salty1962 Wrasse and SPS Lover R2R Supporter Reef Squad R2R Excellence Award Build Thread Contributor Partner Member 2018

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    Great Info, Thx for posting!
     
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  9. mdbannister

    mdbannister Ahh...the Reef Life Staff Member Team R2R R2R Excellence Award SCMAS Member Build Thread Contributor Article Contributor Partner Member 2018

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    Indeed! Very helpful!
     
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  10. Mark Gray

    Mark Gray Valuable Member R2R Supporter Build Thread Contributor Partner Member 2018

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    Good info
     
  11. Flippers4pups

    Flippers4pups Fins up since 1993 R2R Supporter Reef Squad R2R Excellence Award Build Thread Contributor

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    Flippers up! Nice info, Dana!

    Thank you.
     
  12. JonasRoman

    JonasRoman Well-Known Member

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    @Dana Riddle , thanks for a post with valuable and high density of knowledge.
    Can i ask you a question?:

    You do not mention PUR? Is it correct that PUR is that part of the PAR which falls within absorption-spectra of chlorophyll a, c,, or at least that part of the PAR which leads to Photosynthesis? In that case, PAR is very exaggerated by some, as if we for instance have a lot of green and yellow light (with low photosynthesis activity, as with some white diods for instance) it must be compensated with more PAR to get equal/proper amount of PUR. Or? Why does we always talking about PAR, shouldn't we always talk about PUR?, thus the interesting part of the light, the PAR with photosynthesis activity so to speak. Why do we not see the different brands showing these figures? I realize that is is more difficult to measure as it should require som selective measure of different wave-length-interval, or?...I realize it is more easy to measure the whole spectrum, 400-700, but says not so much...If we have to measure PUR, how do we do that? With a prisma which is divided the wavelengths and then a light measure of each wavelength? thus not a photometer, but a photospectrometre....Are my thoughts correct??:)

    Thanks in advance for answer

    regards
    Jonas Roman
     
  13. Dana Riddle

    Dana Riddle Well-Known Member Staff Member R2R Supporter Build Thread Contributor Article Contributor Expert Contributor

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    Yes, you are correct. I should add several definitions to that list (and will as soon as I can figure out how to modify that post.) I have two Ocean Optics spectrometers and a LS-Cal light source that can be used to make measurements/ calculate PUR. Need to get those items unpacked and get the new lab completed.
     
  14. JonasRoman

    JonasRoman Well-Known Member

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    Thanks:). I will follow your thread with great enthusiasm and interest:)
     
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  15. Dana Riddle

    Dana Riddle Well-Known Member Staff Member R2R Supporter Build Thread Contributor Article Contributor Expert Contributor

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    I added several definitions to the glossary.
     
  16. Mark Gray

    Mark Gray Valuable Member R2R Supporter Build Thread Contributor Partner Member 2018

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    Nice thank you guess it's time to buy some spectrometers.
     
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  17. Mark Gray

    Mark Gray Valuable Member R2R Supporter Build Thread Contributor Partner Member 2018

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    Hi Dana could you give me a recommendation for a spectrometer This is one thing that I have not tried or even looked at
     
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  18. Abhishek

    Abhishek Valuable Member R2R Supporter R2R Excellence Award

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    Amazing info .. thanks for posting .

    @Dana Riddle - Would like to know what's the ideal photoperiod for an acropora reef tank if PAR is kept within 250-350 and enough water flow provided with stable alkalinity?
    Should the photo period vary with the different types of lights used if PAR remains the same? My specific reef is all acros with PAR adjusted to your suggestion using hobby grade Apogee meter but lit only by radium 250 watt halides x 2 .
    Its currently running at 5 hours a day but wanted to know whats the ideal PAR photoeriod should be .

    Regards,
    Abhishek
     
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  19. Dana Riddle

    Dana Riddle Well-Known Member Staff Member R2R Supporter Build Thread Contributor Article Contributor Expert Contributor

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    PASCO Scientific has some low cost (but not inexpensive) spectrometers. These are about 1/3 the price of the Ocean Optics specs I have, but I've heard good things about them. Let me know if I can be of further assistance!
     
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  20. Dana Riddle

    Dana Riddle Well-Known Member Staff Member R2R Supporter Build Thread Contributor Article Contributor Expert Contributor

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    I used PAR of 300 and 10 hour photoperiod to calculate a DLI, and arrived at 10.8, which some be fine. Make changes to photoperiod slowly and watch your corals for any negative signs. The Radiums should generate good coloration and, yes, their PUR will be different from other light sources. Just how much of a difference this makes needs to be investigated, something I could do once the new lab is completed.
     
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