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Pendant LED lighting has become increasingly popular in the last two years. The Orphek DIF 50 XP Pendant provides a means to effectively illuminate both shallow and deep tanks (depending on the lens used) with enough PAR/PUR to support corals and other photosynthetic life. Orphek’s engineers have given the Orphek DIF (diffused) 50 Pendant a makeover by introducing a new multi-chip LED which incorporates some high range UV along with some added red. The UV starts out at 380nm, peaks sharply to 410nm, and rapidly falls off. UV radiation in this range is safe for humans according to NASA standards. It also mimics the wavelength of chlorophyllA and B as the spectrograph below will show. This is the first LED fixture that I am aware of that produces blue light without the use of energy wasting blue LEDs which have very low lumens per watt ratio. The Orphek DIF pendants are very versatile. Depending on the lens used, they can be used for cube tanks, large systems, and aquaculture facilities.
The Orphek DIF 50 XP housing is manufactured from high quality extruded aluminum and features a built in Mean Well LPF-60-36 constant current driver with EMI filtering and auto over current shut off. The voltage and current are regulated to within +/- 0.5 percent. The driver itself has a two year warranty. All removable covers on the DIF 50 XP incorporate silicone "O" rings which protect the unit from the environment.
The business end of the pendant features a custom ground optical quality lens and you can order the pendant with your choice of four lenses depending on your application. The lenses are available in 45, 60, 90, and 120 degrees and are easily changed by unscrewing the lens holder and replacing the lens. This feature makes the DIF 50 XP very versatile so if your requirements change, using a different lens can easily accommodate a new application. As an example, a pendant equipped with a 120 degree lens placed 12 inches above the water line will cover a 26 x 26 inch area. Lower degree lenses will cover less area but offer deeper penetration.
Lenses are easily removed should you decide to change to a different lens.
The massive heat sink used on the DIF pendants is
one solid piece of extruded aluminum and requires no cooling fan.
The electrical components are protected within a die cast aluminum enclosure (right photo),
and further protected by the pendant cover (left photo). This is not a cheaply
The LEDs used in the DIF 50 XP are manufactured in the United States by high quality LED suppliers. The intensity this chip provides is advertised to be equal to a 250 watt metal halide lamp’s PUR range, the spectrum most desirable for coral and other photosynthetic life. The chip features:
60% 18K white – 30 LEDs
10% 410nm/chlorophyll A peak – 5 LEDs
10% 430nm/chlorophyll A peak – 5 LEDs
10% 453nm/chlorophyll B peak – 5 LEDs
6% 585nm/coral fluorescence – 3 LEDs
2% 660nm/chlorophyll A – 2 LEDs
2% 640nm/chlorophyll B – 2 LEDs
Fifty, one watt LEDs are used in the multichip
In the rare event of a LED failure, the chip can be replaced by the user, no soldering is required. The pendant can also be ordered in any LED configuration you desire. More red, less red, more UV, less UV, more white, less white, etc. Unlimited options are available. The pendant is not dimmable as is, but as an added option, plugs can be installed that will plug in to the light modules for GHL Profilux, Apex, and Neptune controllers. The pendants are also available in 30 and 100 watt XP configurations. A ¼" eye bolt and quick link are included for suspending the fixture above the aquarium. I chose not to suspend from the ceiling but to fabricate a support from 1" EMT electrical conduit. For those wishing to do this, the materials required can be found at Home Depot and most hardware stores. I have less than 25 dollars invested in this support.
Two DIF 50 XPs with 60 degree lenses. The prototype support constructed
for the review will be spray painted satin black and the power cords will be
nylon tie wrapped to the conduit.
The Orphek DIF 50 XP measures 12.48" long by 8.66" in diameter and weighs 9.9 pounds.
With LED lighting, PAR can be somewhat confusing as the definition of PAR is any light in a specific frequency range which is between 400nm-700nm. PUR is the usable portion of PAR which promotes coral growth and falls between two ranges, 400nm-550nm, and 620nm-700nm.
The Orphek DIF 50 XP covers these areas very well as the below spectrograph will show.
The red LEDs (640 and 660nm) used in the pendant nicely cover the chlorophyll A range. No energy is wasted on unneeded wavelengths.
Looking at the graphic below, you can see that the DIF 50XP mimics the wavelength of deepest penetration in sea water.
Graphic courtesy of Ushio Electric
A Word About How PAR Data Is Measured.
PAR is measured as PPFD (Photosynthetic Photon Flux Density) in micromoles/m2/sec. A PAR reading of 100 micromoles/m2/sec at the bottom of the tank will provide enough of an upward light gradient to satisfy a wide range of corals that we commonly keep. Multiple fixtures will provide regions of overlapping light distribution which will provide an additive effect thereby increasing the light intensity and area covered. For the review I used two DIF 50 XP pendants with 60 degree lenses on a 38"L x 16"W x 22"D aquarium. The tips of the lenses are 13" above the water. I used the latest model Apogee MQ-200 Quantum Meter and sensor for measuring PAR. The spectral response of the Apogee Quantum Sensor measures the PAR wavelength between 400-700 nanometers. The Quantum sensor is not flat across this entire range. Between 400-460nm, it will read between 10 to 60 percent less (depending on wavelength) than what is actually present. The spectral response curve of the Apogee Quantum Sensor shown below will depict this. Since the Orphek DIF 50 XP’s highest peaks occur at 430 and 453nm, the PAR reading at 453nm would actually be 20 percent higher than what was measured and the 430nm peak would be approximately 35 percent higher. Since there is no way I can isolate and measure these peaks, consideration must be given to the PAR readings taken. Based on the spectral response chart shown directly below, I would estimate the actual PAR values to be 20 percent higher than what was measured based on the wavelengths the DIF 50 XP produces.
The below PAR readings were taken using all four available lenses. The Apogee spectral curve compensated PAR values will also be shown in the charts. Readings at 12 inches were not taken with the 45 and 60 degree lenses as these lenses were primarily designed for lighting deeper tanks.
The above charts will give you a good idea of which lens to use on your particular application and tank size.
A note on measured PAR values
Comparing PAR values of LED lighting systems that have a high PUR ratio can be misleading when compared to PAR values of metal halide lamps. A typical 10 or 14K metal halide lamp’s spectral response wastes much energy in wavelengths not required for growing corals and can promote nuisance algae growth if dissolved nutrient levels are high. A spectrograph of a typical 10 and 14K metal halide lamp is shown below.
Graphic courtesy of Ushio Electric
The unneeded wavelengths actually add to the overall PAR value of the lamp. Based on this, I feel that a PAR of 50-60 of a LED fixture that favors the PUR wavelengths would be equal to a PAR of around 150 in a typical 10 or 14K metal halide lamp. Compare these charts to the Orphek spectrograph for a visual of what I have stated and you will see there is no wasted energy spent in unneeded wavelengths.
Power Consumption (For One DIF 50 XP Pendant)
Volts – 123
Based on my energy provider’s rates, I could run one DIF 50 XP with a photo period of 10 hours per day for $1.50 per month. This results in a substantial savings in energy considering the light output of this fixture. A 250 watt metal halide/HQI lamp would cost approximately $7.50 per month and that does not include a 6-12 month lamp replacement cost of approximately $100.00 per year. Doing the math, the halide lamp would cost approximately 190.00 per year to operate versus $13.50 per year with the DIF 50 XP. If a chiller is required with the use of metal halides, this cost will rise considerably. Using this as an example, a savings of $175.00 per year would pay for this particular LED pendant in four years. Similar savings will result with any capable LED system, not just the Orphek DIF 50XP.
Visible color and brightness does not mean much if the lights cannot promote photosynthesis in our corals. Corals might look great under incredibly blue light but it isn’t always beneficial for coral growth. The DIF 50XP does not appear as blue as the spectrograph would suggest, but rather a very light shade of purple. Coral highlights are pronounced but not overly done or gaudy in appearance.
A shop in Norway using DIF 100XPs over the frag tanks.
Above photos courtesy of Coralsno (Norway)
I started with the 120 degree lens and found that this would not provide enough PAR/PUR for my deeper tank of 22 inches. The 120 degree lens is more suited for shallow frag tanks or smaller aquariums. A 24" x 24" cube tank would be an ideal candidate for this lens. Using the 90 degree lens provided plenty of PAR/PUR to promote photosynthesis but was not quite enough to cover the entire 36 inch length of the tank. Experimentation proved that two DIF 50 XPs would be needed to cover the entire tank while providing plenty of PAR/PUR for coral growth. I decided to go with two pendants using 60 degree lenses. After experimentation with the correct height, this proved to be an ideal matchup for the review tank.
Performance is where the Orphek DIF 50 XP really starts to shine. With LEDs, there are two types of fixtures; those with a tight LED array which mimics halide lighting very well and those with LEDs spread across the entire surface which tend to look more like T5 lighting. The DIF 50 XP falls into the first category as the shimmer effect is equal to or better than metal halide lighting. The red diodes in this fixture are tightly placed near the center leading me to believe that only the area directly under the red LEDs would benefit from the reds. In actual use, the red light actually spreads evenly across the entire tank. This obviously is due to the excellent optical quality lenses used in the DIF series of pendants. The color pop they give to red pigmented corals is beautiful and Orphek does this with only four red LEDs. The blue spectrum is still intense enough to give greens amazing pop, and the whites help to balance out the whole visual effect. As to the effects of the UV LEDs, they do contribute nicely to the coral’s ability to floresce.
I found the Orphek DIF 50 XP to be of high quality and a very versatile LED fixture. The components and materials used are first rate as well as the quality of light it produces. At normal hanging height there is no heat transfer to the water. Heat is evenly dissipated through the aluminum heat sink fins which wrap around the entire housing. You won’t find any gimmickry used here such as the ability to change colors by programming. In my opinion a feature like this may be a waste of money. What you will find is a LED fixture that has been carefully fine tuned to provide the PAR/PUR values needed for photosynthetic life. The only down side to the DIF 50 XP is not having the ability to dim without the use of a controller.
In the three weeks I evaluated the Orphek DIF 50 XP, I did notice a reduction of nuisance algae growth in the tank. Although I have little nuisance algae to begin with, the time span between cleaning the glass did increase. My corals expanded more, and have shown much better coloration and florescence than they did with a previous 10K LED fixture I had been using.
Below are a few photos of corals in the author’s tank under the Orphek DIF 50 XP Pendants.
Montis, Finger Leather, and Star Polyps
A small Bubble Tip Anemone
Additional information and photos can be found here:http://orphek.com/led/orphek-products/dif-pendants/ http://orphek.com/led/2012/03/corals-under-orphek-dif-100-xp/