Lighting the Reef Aquarium By Dana Riddle

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  1. Orphek

    Orphek Orphek- Aquarium LED lighting R2R Supporter Platinum Sponsor

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    We invite you all to talk about LIGHT. Come share your knowledge, your thoughts and experience with us!
    original source link : https://orphek.com/lighting-the-reef-aquarium/

    By Dana Riddle
    There are many aspects involved in successfully husbandry of a reef aquarium, not the least of which is lighting.
    This article is the first in a series that will examine this important parameter and will discuss why lighting is important, especially if the goal is to maintain photosynthetic organisms such as many coral and clam species as well as algae.

    With this understanding, along with patience and dedication, it is possible to maintain a spectacular piece of a reef within your home.

    The focus of this article will be on corals and why we should provide the proper amount of light – too much light can be detrimental and, in some cases, is as bad as too little light.

    But first, why do we need to properly illuminate a reef aquarium at all?
    The answer is the due to the presence of microscopic ‘algae’ living within many healthy corals’ tissues. These are generally called ‘zooxanthellae’ and are of the genus Symbiodinium. See Figure 1.
    [​IMG]
    Figure 1. A zooxanthella cell from a Favia stony coral. An electron micrograph taken for the author at the University of Georgia.

    Years ago (in the early 1960’s) there was only one Symbiodinium species described – Symbiodinium microadriaticum.

    Our knowledge has certainly increased over the years, and today we know there are at least nine described Symbiodinium species, with hundred of ‘types’ called clades (a clade is a group of things with a common ancestor.)

    As any terrestrial gardener knows, there are ‘sun plants’ and ‘shade plants’ and this refers to the amount of light tolerated.

    For instance, Marigolds prefer full sunlight, while Wisteria do not and are best suited for shaded areas.

    The same is true for the zooxanthellae populating corals – some corals and their symbionts do well in high light while others are best suited to lower light conditions.

    Fortunately, it is possible to find a compromise in an aquarium resulting in the successful maintenance of ‘sun’ and ‘shade’ zooxanthellae and their host corals.

    There are two methods to achieve success as it relates to lighting.

    There is the ‘copycat’ method where one mimics lighting used over a successful aquarium. This approach can certainly lead one to a nice aquarium, one full of thriving corals. But it does have drawbacks – no two aquaria are exactly alike and details that seem minor can have major – sometimes negative – impacts. The other method is one that involves a ‘scientific’ approach where light intensity is measured, and corals are placed in appropriate places within the aquarium.

    There are various ways to measure light intensities.
    The least expensive way is through use of a lux meter. Lux is a unit of illuminance and is equal to one lumen per square meter. Lux is a universally recognized measurement unit and is part of the International System of Units (SI.)

    Maximum sunlight (at noon on a cloudless day) is about 100,000 lux. Lux is not the best way to measure light in an aquarium since a lux sensor measures light skewed towards the green portion of the spectrum.

    A much better way is to measure Photosynthetically Active Radiation (PAR) through use of a quantum meter.

    This meter reports the number of light particles (photons) falling upon a given surface area (usually one square meter.)

    This number of photons can be enormous, so it is reported as microMol per square meter per second (µmol·m²·sec.)

    Sunlight at full strength is about 2,000 µmol·m²·sec. Quantum meters are generally more expensive than lux meters.

    However, it is an invaluable tool – if its purchase is beyond the means of the aquarist, perhaps the local fish club can purchase one for members’ use.

    We know lighting is a critical part of a successful reef aquarium – why would one ignore measuring it?

    How many successful hobbyists ignore measuring other parameters such as salinity, pH, alkalinity, or calcium? Sure, it can be done but leaves a lot to chance…

    Next time, we’ll begin an examination of various light measuring devices.



     
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  2. Orphek

    Orphek Orphek- Aquarium LED lighting R2R Supporter Platinum Sponsor

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    Lighting the Reef Aquarium: Part II
    October 16, 2018
    Measuring Light Intensity
    By Dana Riddle
    original source link :https://orphek.com/lighting-the-reef-aquarium-part-ii/
    If I were to ask reef aquarium hobbyists these questions, their answers would likely be as follows:

    Q: What is the Specific Gravity of the water in your tank?

    A: 1.025

    Q: What is your calcium concentration?

    A: 400 milligrams per liter (or parts per million)

    Q: What is the highest light level in your tank?

    A: I likely won’t get an answer.

    Why? It is probably due to several thing:

    1. Lighting can be a complicated issue, and there isn’t a universal correct answer.

    2. Measuring light intensity requires a meter, and they are sometimes expensive.

    3. Measuring light intensity isn’t very exciting!

    I’ll try to ‘un-complicate’ the issue of lighting in this and future articles.

    As for the expense of a meter, a fish club could pool members’ resources and purchase one.

    Not much we can do about making light measurements exciting – but they are no more boring than calcium or alkalinity tests.

    Many light sources (such as fluorescent, metal halide and mercury vapor lamps) can lose intensity over a period of months.

    Monitoring their output is important and can be used to time lamp replacement.)

    Generally, light-emitting diodes (LEDs) do not lose a great deal of intensity over their life spans (years under best of conditions.)

    In this installment, we’ll examine the different ways to measure light in an aquarium, and the pros and cons of each.

    These devices are called Lux Meters and Quantum (or PAR) Meters.
    [​IMG]
    Figure 1. A few of the light measuring devices in the author’s laboratory.

    Lux Meters
    Pro: Relatively inexpensive.

    Cons: Sensor is most sensitive to green light, and ‘sees’ light that is important to

    photosynthesis poorly (such as violet/blue and red light.)

    Lux meters can be the least expensive method of measuring light in an aquarium, but the sensor responds best to green light (its response is photometric and corresponds to those light wavelengths that the human eye perceives best but are least effect in promoting photosynthesis.) A lux meter’s sensor must be waterproof, and preferably cosine corrected (meaning the measurement is not greatly affected by the angle of the sensor in relation to the lighting source) and have the ability to read to at least 100,000 lux (the intensity of full-strength sunlight.) Measuring light with a lux meter is better than no measurements at all. Conversion of lux to Photosynthetically Active Radiation (our next subject) is possible if conversion factors are known.

    Quantum or PAR Meters

    Pro: Used in peer-reviewed scientific journals and by serious hobbyists, making comparisons easy.

    Most sensors are cosine-corrected, waterproof and designed to deliver accurate results when submerged in water.

    Some have good responses to LED lights.

    Con: More expensive than lux meters.

    Quantum meters were used mostly by researchers, and professional aquarists until the late 1990’s when one costing about $200 US was introduced. Since then, PAR measurements (correctly called PPFD for Photosynthetic Photon Flux Density) have become the standard for reporting light intensity in an aquarium. Since the energy level of a photon is not important in photosynthesis (a blue photon promotes photosynthesis as well as a red one once it is absorbed by photopigments such as chlorophyll) quantum meter reports the number of photons across a bandwidth of about 400 nanometers to 700 nanometers (a nanometer is one-billionth of a meter) without regard to their energy levels.

    PPFD is reported in units of microMol per square meter per second, or µmol·m²·sec. A quantum meter should report light intensity to at least 2,000 µmol·m²·sec (which is about the intensity of full-strength sunlight.)

    There are other ways to measure light intensity, such as a radiometer (which reports in radiometric units of watts or micro-watts.)

    There are very few scientific papers concerning corals that use radiometric units, and none in hobbyist literature, so we can disregard this method.

    Now that we know about methods of measuring light, we’ll next look at light intensities on a real reef.

    One might ask – “Why bother measuring light, since corals can use all the light they can get!

    I see photos of corals exposed to air and intense light at low tide and they’re doing fine!” We’ll examine why this is wrong in the next installment.
     
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  3. TexasTodd

    TexasTodd Well-Known Member

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  4. Orphek

    Orphek Orphek- Aquarium LED lighting R2R Supporter Platinum Sponsor

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    Lighting the Reef Aquarium: Part III
    The Myth of Corals Requiring Unlimited Amounts of Light

    By Dana Riddle

    I had the pleasure of living on the Big Island of Hawaii for almost two decades and took every opportunity to study the natural reefs there (See Figure 1.) One of my projects involved the determination of light required by photosynthetic corals (note: required versus tolerated.)
    [​IMG]
    Figure 1. This shallow tide pool, just inches deep, contains beautiful Hawaiian corals. Experiments were conducted on animals found here.

    At the time, getting permits required by the State of Hawaii was relatively easy, and once these were in hand, the project could proceed. Determination of rates of photosynthesis requires all the equipment normally found in a wet lab, plus some highly specialized instruments.

    The first of these is a quality Quantum (or PAR) meter (discussed in some detail in Part II of this series.) The second is a Pulse Amplitude Modulation (PAM) Fluorometer (See Figure 2.)
    [​IMG]
    for the entire post read more: https://orphek.com/the-myth-of-corals-requiring-unlimited-amounts-of-light/
     
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  5. Orphek

    Orphek Orphek- Aquarium LED lighting R2R Supporter Platinum Sponsor

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    Lighting the Reef Aquarium Part 4
    Light Requirements of a Coral Genus Often Found in Reef Aquaria
    By Dana Riddle

    In previous installments, we have discussed how to measure light intensity, reviewed light requirements of a Hawaiian coral, and discussed terminology. This time, we’ll look at light requirements of a coral genus often found in reef aquaria – Acropora.

    Acropora is a pandemic genus and is found in Atlantic and Pacific Oceans. There are XXX species described and can occupy shallow to very deep waters. It is a common belief that small-polyp stony (SPS) corals’ zooxanthellae require high intensity light to survive. Is this true? To answer this question, we’ll revisit issues of photobiology.

    As we discussed previously, Symbiodinium species and clades require a minimum amount of light, and this is called the Compensation Point. On the other hand, the Saturation Point is when the rate of photosynthesis does not increase with increasing light intensity. As reef hobbyists, it is our goal to exceed the amount of light required for the Compensation Point (necessary!) but not pass the Saturation Point (Note: This is for photosynthesis – the amount of light required for expression of color in corals often exceeds the Saturation Point. We’ll discuss this in the future.)


    For the entire post read more:https://orphek.com/lighting-the-reef-aquarium-part-4/
     
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