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Aquarium
Lighting
Scroll down for LEDs Lighting is one of the more important factors for the aquarium. Our focus is saltwater aquariums and more specifically a basic mixed reef tank. The animals usually include what are generally considered "easy-to-keep" corals, fish, and invertebrates (shrimp, crabs, anemones, snails, etc.). Many organisms such as plants, algae, corals, and some bacteria synthesize food directly from carbon dioxide using enery from light - photosynthesis. It is thought that fish depend on light, much like humans, for immune function and general health. Lastly, reef keepers enjoy the bright look and varied colors and shapes in their tanks illuminated by the right lighting. Since most of the animals kept in the hobby live in and are collected from shallow, atoll coral reefs on and near the equator, we start by analysing the quantity and quality of natural sunlight found there. Basic physics teaches us that light has a wave-particle duality. Wave properties measured in wavelength and frequency (spectrum, color), and particle properties (photons, intensity).
Quality of
light - spectrum, color, appearance, Kelvin (K), CRI,
CCT
There are two systems of measurement commonly used to describe the color properties of a light source: “color temperature” (K for Kelvin rating) which expresses the color appearance of the light itself, and “color rendering index” (CRI), which suggests how an object illuminated by that light will appear in relation to its appearance under other common light sources. Sunlight is said to have a CRI of 100.
Photosynthetic light
below the water surface
There is some evidence though, and a belief (a quite strong belief for some) that there are two spectrum "spikes" most or more important for coral growth and color. One broad spike in the purple/blue 400 to 500 nm range and a narrower red spike around 660/670. Lastly, some adhere almost dogmatically to the belief that the blue range is the most important spike, in part because the blue spectrum light best penetrates water, and a belief they are keeping "deep water" corals - those that live in and are collected from depths, 15 to 60 feet. "This experiment's results suggest information potentially valuable for hobbyists - that rates of photosynthesis were essentially the same under these two distinctly different light sources. Other than aesthetic value, there appears to be no advantage, photosynthetically speaking, in using high Kelvin lamps." Dana Riddle, Advanced Aquarist Magazine, Feb 2002 |
Now, let's turn to our typical mixed reef system and the available light sources in the hobby. Artificial lighting companies and hobbyists try to mimic mother nature and even try to do her one better.
In general,
we are looking for at least 100 PAR (or 3000 lux)
intensity on the sand bed
(bottom of the tank)
and the required color spectrum
for
the animals.
Stagger corals by placing them on your live rock aquascape at
depths (low/sand bed, mid tank, and high) according to their needs. Higher in the tank for more
light intensity. Of course, the height above the water surface
of the lighting system will influence PAR values and coverage.
Most clams, most SPS corals, and carpet anemones for example require high light intensity.
Color:
The various wavelengths within a given light source—its “color
makeup”— can vary greatly and it will still appear white.
Coverage:
A 250W MH covers a tank surface area of 36"X30".
A 36" T5 (6tube x 39watt) fixture covers an area of 36"x24"
A 24" LED fixture with 90 bulbs covers an area of 24"x18"
Many reefkeepers employ a 12-hour photoperiod. With multi-light systems, you can use timers to vary the intensity by varying the number of lights on at any one time. Usually, one bulb comes on for an hour, then all bulbs for 10 hours, then one light is left on for an additional hour while the others are turned off. This is one method to duplicate the sun passing over the reef.
Fixtures are made-up of bulbs, reflectors, and electronics.
Lighting fixtures can be built into
canopies, hung from the
ceiling or light stands, or placed directly on the tank walls
with fixture stand attachments. Combo systems have mixes of bulb
type, intensities, and colors in the same fixture.
Consider PAR per watt, PAR per dollar, operating costs, coral growth rates, and your personal preference for the appearance of your tank under a certain lighting scheme. Also consider usable PAR, PUR, PPFD, and CRI.
Color:
The color temperature of light is the ratio of red to blue light
waves measured in degrees Kelvin (K). At 6000 degrees (K), the
ratio between red and blue is equal. The higher the content of
blue light waves, the higher the color temperature. Blue light
penetrates saltwater best and corals most benefit from 400-420 nm
(more violet and near UV) and 440-470 nm wavelengths of blues
(blue at 470, and royal blue at 450.
Coral Health and Color:
In nature, many corals have made adaptations to the the effects
of harmful UV-A and UV-B rays. Corals have developed protective
pigments that are often blue, purple, or pink in color. Most
corals that contain these pigments come from shallow waters
where the amount of UV-A and UV-B light is higher than in deeper
areas of the reef. Corals can lose their color due to the
low light levels and blocked UV in an aquarium -- doesn't mean
they are unhealthy.
Corals may grow more brown under low light intensity and lighten under higher light levels.
Corals may show more colors with exposure to blue spectrum lighting. Some corals are collected from depths of 15 to 65 feet where mostly all but blue wavelengths have been filtered out. Why not all blue then for our tanks? Many just don't like the look, so a popular combination is part bright daylight wide spectrum white and part blues (aka actinic).
General System Comparison
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| LED (light emitting diodes) |
LED Directory - System Manufacturers, Retailers, Resellers and
DIY
(We will try to identify the OEMs.
A basic, then more detailed comparsion matrix is in the works.
Please check back.)
Evolution
Fredlighting
IceCap
KEY
Orbitec (note, patent issues)
PFO (Solaris, Galileo models)
ReefFanatic
RIO
Sfiligoi
Shanhai
Shenzhen Jiangjing Lighting Co., Ltd. (OEM)
Superstar LED Lighting Limited
Weipro
Wingo
Won
LED
bulbs and chips
Eco-Lamps, Epistar, CREE,
Osram, Philips Luxeon,
SemiLEDs,
BridgeLux
Bulbs and chips from Taiwan:
The Taiwan government-sponsored Industrial Technology Research
Institute (ITRI) has joined with the 14 makers of LEDs and LED
chips. The companies are: Epistar, Formosa Epitaxy, Arima
Optoelectronics, Opto Tech, Tyntek, Ledtech Electronics, Unity
Opto Technology, Para Light Electronics, Everlight Electronics,
Bright LED Electronics, Kingbright, Lingsen Precision
Industries, Ligitek Electronics and Lite-On Technology.
Spectrum and color
Note that blue and royal blue are significantly different.
3500K is only
slightly bluer than halogen and feels like you're next to a cozy
fireplace.
6500K feels
like you're under a cloudless arctic sky.
Optics
Optics affect coverage and spot-lighting. Some fixtures have interchangeable lenses.
Narrow optics
can produce high PAR but also spot-lighting, shadows, color
variation, and even the chance of burned corals.
Also, coverage/spread can be poor with high PAR directly under
the lights, but unacceptably low PAR on the fringes of the light
pattern.
Common LED OEM models.
PAR Measurements
AquaIlluminations LED (AI70watt) test, recently reported by a hobbyist, 2 fixtures with slightly overlapping light
6" - 1650
12" - 1370 (water surface)
16" - 915 (4" water depth)
19" - 690 (7" water depth)
24" - 560 (12" water depth)
ReefKoi says, "When we did real world PAR testing over a reef aquarium we mounted the lights ~5″ above water and got 965 at the surface, 500+ 5″ down and 200+ 19″ deep and 115 at the bottom 23″ down…….I think its respectable, considering the wattage used? I mean a 150 HQI would be lucky to get 20 PAR at 23″ deep I’m guessing."
ReefLEDLights says, "A 250 watt 10K XM light produces about the same PAR as a 400 watt Radium. This is why I claim such a range. The hard numbers are 48 XR-E LEDs on a 8″x24″ heatsink using 80 degree optics will produce 296 PAR at 24″, when driven at 700mA. When driven at 800mA the same fixture will produce 323 PAR. A 400 watt Radium produced 310 PAR at that distance and the 250 watt 10K XM produced 305 PAR."
Sanjay Joshi says, "Based my experience with light measurements and 20+ years of keeping corals I have found that light levels of 100 PAR, at the bottom of tank is usually more than enough to allow keeping a wide range of corals successfully. Incidentally, my personal 500G (84"LX48"WX30"H) tank lit by 3 400W Ushio 14000K lamps in a Lumenarc reflector mounted about 12" from the water surface has PAR readings at the bottom ranging from 80-120. With PAR levels averaging 100 at the bottom of the tank, there is enough of a light gradient to allow keeping high light loving corals in the top ½ to 2/3rd of the tank, with lower light corals scattered in the lower half. Most acropora and other light loving corals will thrive at light levels of 300-400."
Coverage or spread (refer to manufacture charts)
A 250W MH covers an area of 36"X30".
A 36" T5 (6tube x 39watt) fixture covers an area of 36"x24"
A 24" LED fixture with 90
1-watt bulbs covers an area of 24"x18"
Spectrum and Color
1 Royal Blue to 1 Cool White will give you a 10-12K look.
2
Royal Blue to 1 Cool White will give you a 18-20K look.
Blue and
royal blue LEDs are significantly different from each other.
Binning
CREE manufactures a range of different LEDs, and the term
"binning" refers to the method that the company uses to sort all
these LEDs in terms of their dominant wavelength (color) and
luminous flux (brightness). The resultant "bin number" is then
used by manufacturers of LED products to specify the color and
brightness of the LEDs they wish to use.
Metal Halide (MH)
An older, mature technology already covered by many sources.
Fluorescent (T5)
Plasma Arc
Plasma Arc Lighting
Natural Sunlight
In our KIS system, NOTHING comes close to natural sunlight. Like flowers opening up, the coral polyp extension and detail that can be easily seen by the naked eye is far greater than any artificial light source.
More indepth treatment of lighting here.