Introduction and Background



When initially starting this adventure, the goal I had in mind was to investigate lamps that would be suitable for use in my tank when the time came to change metal halide lamps. At the time I found little information available on the 250-watt single-ended (SE) metal halide (MH) lamps that I was using. Prior to actually laying out the funds to buy the same type of lamps again, it seemed reasonable to research a wide variety of products that were available on the market. That way, I could be certain that the product that I purchased best fit the needs of my tank.

In the beginning, some fellow reef enthusiasts assisted my search for suitable replacement lamps. A few friends lent me some of their extra lamps, and I was also able to borrow a PAR meter from another associate. After using the new equipment, I took readings and shared my findings by posting an "innocent" picture or two on Reef Central. Thereafter, my project took on a life of its own. Soon, people were e-mailing me and asking me to post more information on other lamps. People offered to send me a lamp or two to test. While testing more lamps, I found some ways of testing to be better than others. I found myself with results that left me with questions that needed to be answered. I realized that I had lighting questions that I needed clarified so that I could better understand the results that I was seeing and, in turn, have the ability to explain my findings to others. I wondered about the reasoning as to why measuring photosynthetically active radiation (PAR) was better than measuring lux. In an effort to seek a fuller understanding, I spent a great deal of time researching, testing and discussing basic lighting with people more knowledgeable than I. This resulted in a massive thread on Reef Central encompassing some 50-odd pages, and boasting 1300 posts, wherein I discussed all of the lamps that I tested, along with my notations regarding each product and my final test results. Such a thread is definitely a large undertaking for any aquarist to comprehend. I decided to write the present article to summarize my findings in an effort to help reef aquarists better understand what I tested, and to share my results.

What Was Tested



I tested just about every lamp and ballast that I could get my hands on during the testing time. Whatever I received made it onto the final list. A total of 21 lamps and 8 ballasts were used, as shown in Table 1 below. Almost all of the lamps were tested on every ballast. I had to return a few lamps (and one ballast) to the person who lent them to me, as they needed to be used on the person's tank. Therefore, not every combination was tested. Still, each ballast/lamp was tested against enough lamps/ballasts that their performance tendencies are readily seen; whether being judged on its own or against other similar equipment.

Table 1 � Lamps and Ballasts Tested

Lamps Tested Ballasts Used Aqualine Buske 13000K PFO 13000K ARO (Hellolights) Electronic Ballast AquaConnect 14000K Radium CoralVue Electronic Ballast Blueline 10000K Sunburst 12000K Blueline E-Ballast Electronic Ballast Blueline Super White Sun Aquatics 10000K EVC Ballast CoralVue 10000K Sun Aquatics 14000K IceCap Electronic Ballast CoralVue 12000K Sun Aquatics 20000K PFO HQI Ballast CoralVue 15000K Ushio 10000K PFO Standard Ballast CoralVue 20000K XM 10000K Reef Fanatic Ballast EVC 10000K XM 15000K Hamilton 14K XM 20000K Iwasaki 6500K

Ballasts appeared to operate the same regardless of how long they had been used. I found no difference between one that was fresh out of the box and one that had been run for months, or even years. That led me to believe that there was no break-in period for metal halide ballasts.

How These Tests Were Conducted



I should state up front that I am a hobbyist; I'm not an electrical engineer, nor am I involved with the manufacture of lighting equipment. I conducted these tests solely to satisfy my own curiosity, out of my enthusiasm for the hobby. When these tests were started almost no information was available for 250-watt SE metal halide lamps. With that said, I tried to get as much pertinent information as I could to answer my question on how different 250-watt SE metal halide lamps performed. In turn, I wanted to share my understandings with other hobbyists so that we could make a better, more informed decision about what types of lighting we purchase to support our systems. As a side note, all of the lamps that I tested were burned in for at least 120-150 hours before being tested. Additionally, all lamps, excluding the Ushio, AB and Blueline Super White, were new at the time of testing. The remaining lamps had roughly six months of use on them (approximately 1600 hours).

It's interesting to note that during the first 100 hours of burn-in time, the halides in the arc tube settle. I found that during the first 100 hours of burn-in time, the amount of light emitted from the lamp was higher (by approximately 10% - 20%) than it was after breaking-in the lamp. It seems reasonable to conclude that the level of light emission stabilizes over time. This is an important note for the reefkeeper when changing lamps. It has been my experience that, in most instances, the measurable output of lamps after a 10-14 month period is nearly 10-20% less than their initial emission. This leads me to believe that if the reefkeeper does not carefully acclimate his corals to new lighting variables, then the lower output of the older lamps, coupled with the higher (albeit temporarily) output of the new lamps, enhances the possibility of a coral bleaching event. Is it no wonder that people so often lose some of their prized acroporids to bleaching after completing a lamp swap?

After a few short tests that were done over my tank (results on this RC thread), it was painfully obvious that a separate environment to test the lamps was needed. This environment would need to be able to produce repeatable results. After much time, and many conversations with other people in the lighting industry, a solution was found. What I wanted was the raw output from the lamp only. Reflector efficiency varies greatly from one product to the other and many people use different reflectors and/or material to get extra output from the lamp, so I decided not to include any reflectors in my testing, as the results couldn't be universally applied if the variable of an assortment of reflectors was involved.

Testing box.

I finally settled on a 2' x 2' x 2' square box (seen above). Its inside was painted flat black to minimize the amount of light reflected back to the sensor. The mogul socket was mounted horizontally, approximately 5" from the ceiling of the box. The quantum sensor (a sensor used to measure PAR) was placed 8" below the center of the arc tube. I chose 8" because this seemed to be a common distance that people keep their MH lamps from the water's surface. To minimize voltage spikes and aberrations, a voltage regulator was used on power from the wall's electrical socket. A watt meter was plugged into the voltage regulator and the ballast plugged into the watt meter.

All lamps, before testing, were powered on and left to burn for at least 20 minutes before any measurements were performed, in order to allow the bulb's output to stabilize. After 20 minutes the sensor was turned on and time was given for a stable reading to be displayed from the meter. Some time (between 2-5 minutes) was given for the reading on the meter to stabilize for at least 30 seconds with no movement. At that time, readings were recorded.

Equipment Used:

Apogee instruments QMSS-ELEC quantum meter with sensor: calibrated for electric lamps

Apogee instruments leveling plate for the sensor

APC Line-R 600 voltage regulator/power conditioner

Electronic educational devices - Watts Up? power analyzer/watt meter

Nikon 995 digital camera used with tripod for pictures

BK Precision 530 multimeter

PAR vs LUX



Many people asked why I used PAR (Photosynthetic Active Radiation) as a way of measuring the lamps as opposed to lux (a photography and media term used to measure light values). Also, many people wanted to know if their lux measurements could be translated into PAR values. In an effort to be as concise as possible on this topic, I'll state that PAR measurement is useful for a number of reasons, the primary one being that it measures the band of light (400nm-700nm) where photosynthesis can occur. A secondary reason is that the light is measured uniformly. Lux readings are geared toward the way humans see light, so greens and yellows are given a higher weight than purples and blues. PAR readings measure nearly the whole visible light spectrum, 400nm-700nm, evenly.

Here are two graphs from Li-Cor, a manufacturer of instrumentation for environmental research. They show how accurate the company's sensors are in reference to an "ideal" curve. In our case, we are interested only in the curve represented by the dotted line.

A graph of how lux is measured:

Graph courtesy of Li-Cor.

A graph of how PAR is measured:

Graph courtesy of Li-Cor.

The graphs clearly show that PAR is a more accurate way to measure lighting for a tank housing photosynthetic organisms.

The graph also shows that getting a lux reading from one lamp is good for comparing it only to the same lamp, or to another lamp with the same spectral plot. Yet, a lux reading from a 6500K lamp could not be equally compared to the lux reading of a 20,000K lamp.

Apogee Sensor Accuracy



The PAR (or quantum) sensor and meter I used are made by Apogee Instruments. They make a reasonably priced sensor that a hobbyist can afford (i.e., under $300). Sanjay Joshi, in his lamp testing, has used a quantum sensor made by the Li-Cor company that costs well over $1000. Naturally, numerous questions were raised about the accuracy of the Apogee sensor used in the test.

The margin of error needed to be considered regarding this sensor. I contacted Apogee and discussed this with a representative, who agreed to send to me two Li-Cor sensors that the company uses for in-house testing. The sensors were first calibrated by Apogee and then shipped to me. After I received the Li-Cor sensors, I took measurements. Two Li-Cor sensors were sent to take measurements with, and to have an average baseline to work from so I could compare them to the Apogee. One measurement with each Li-Cor sensor was taken, and then the two were averaged to produce a value. While the lamp was still lit, a reading from the Apogee sensor was taken and compared to those obtained by the Li-Cor sensors. The table below shows the margin of error the Apogee had when compared to the Li-Cor. Also shown is an adjustment factor. If this factor is applied to the Apogee reading (take the initial reading from the Apogee and multiply it by the adjustment factor), it should correct for any deficiencies of the sensor. All lamps have a slightly different spectral curve, so the error is different for each lamp.

Table 2 - Apogee Sensor Accuracy

Lamp Adj. factor Error % AB10K 1.042700 4.27 XM10K 1.000102 0.01 XM20K 1.054623 5.46 Radium 1.020256 2.03 CV10K 1.014444 1.45 Ushio10K 1.022647 2.26 PFO13K 1.066219 6.62 Iwasaki 1.004403 4.40 BLSW 1.035931 3.59 SUN10K 1.041306 4.13 CV15k 1.062583 6.26 CV20K 1.031709 3.17 BL10K 1.020969 2.10 HM14K 1.041438 4.14 AQ14K 1.027771 2.77 SUNBRST 14K 1.025221 2.52 CV12K 1.076923 7.69 SUN14K 1.026404 2.64

As the chart shows, for such a low price, the sensor is very accurate. On average, it deviates from the Li-Cor sensor by only 3.64%. After taking these readings I felt that, for hobbyists' purposes, the reading from the Apogee sensor was more than sufficient.

Lamp Heat Due to Ballasts



Many people, including myself, have always wondered how much heat is generated from adding metal halide lamps over a tank. I've also wondered how much of a difference fans make in keeping the lamp's heat from impacting the tank's water temperature. To answer these questions, I took measurements and found that different ballasts do vary the amount of heat produced by the lamp.

Temperature measurements were taken the same distance from the lamp as the light sensor was placed - 8". The ballast was turned on with a fan above the lamp, effectively pulling the heat out. After 35 minutes, the temperature 8" from the lamp was taken. To determine the contribution of ventilation to heat generation, we then turned off the fan and, after 10 minutes more (for a total trial of 45 minutes), measured and recorded the temperature again. Ambient room temperature during all the testing was 70°F. The results are found in Table 3 below.

Table 3

Ballast Lamp 0 Min 35 Min 45 Min/No Fan PFO Standard Ushio 70.0°F 83.2°F 90.1°F PFO HQI Ushio 70.3°F 87.5°F 97.2°F eballast Ushio 70.5°F 81.4°F 89.5°F Icecap Ushio 70.1°F 78.6°F 85.2°F CoralVue Ushio 70.3°F 82.1°F 90.6°F ARO Ushio 70.2°F 79.6°F 88.3°F

It seems quite obvious that heat from the lamp can play a significant role in heating the water in the tank. After 45 minutes, the temperature with a fan was approximately seven degrees less than it was with no fan. In the case of the PFO HQI ballast, the ambient temperature in the test box rose almost 27 degrees Fahrenheit when not using a fan to vent excess heat! Proper ventilation, therefore, is a must in any lighting fixture/canopy.

Actual Power to the Lamp



Manufacturers of many of the new electronic ballasts report that they are better suited than magnetic ballasts to power aquarium metal halide lamps due to their sophisticated internal circuitry. In order to test this claim I decided to take some measurements on the wire between the ballast and lamp. The results are given below. While I'm unsure if these results speak better of electronic or magnetic ballasts, the interesting thing to note is that the electronic ballasts varied in their ability to deliver power to the lamp. These two specific lamps were chosen because they were ones that I could track down the power and current specifications as released by the manufacturer.

Voltage measurements were taken using a BK 5390 Multimeter. Current measurements are reflected in TRMS. (RMS stands for Root Mean Square, a technique used to measure AC voltages. True RMS, or TRMS, takes harmonic distortion into account to accurately measure non-sinusoidal AC voltage and current waveforms. On a sinusoidal waveform, RMS and TRMS are the same; therefore, TRMS is advantageous when measurements of non-sinusoidal AC waveforms are required.) The electronic ballasts seem to use the DC sine wave, so both AC and AC+DC measurements were taken. All measurements were taken on the wire between the ballast and the lamp. All ballasts were plugged into a PFO style plug that connected to the mogul socket for the lamp. Measurements were taken where the plug connects to the socket, so all ballasts were measured using the same wire. The lamps were first ignited by the ballast, then left to burn for 20 minutes. At that time, measurements were taken. The results are shown in Table 4 below.

The boldfaced first line in the table below shows the manufacturer's specifications of the lamp. Following are the readings taken while running the lamp on different ballasts. The Standard PFO ballast would not drive or start the Radium lamp, so no information is given for this combination.

Table 4 � Power Profile of Ballasts Tested

Lamp Ballast AC AMP AC+DC AMP Volts kHz Line watts Line volts Radium SPEC 2.80 2.80 95-100 Radium HQI 2.63 2.63 113.50 59.98 Hz 308 117 Radium ARO 3.20 4.79 112.37 76.80 249 117 Radium eballast 2.21 1.95 110.65 80.73 242 121 Radium IceCap 3.20 4.58 109.60 70.47 248 119 Radium CV 2.29 2.01 109.63 67.52 264 119 Radium ReefFanatic 2.28 2.80 131.90 42.03 246 119 Radium EVC 2.37 2.88 115.80 44.68 247 119 Ushio SPEC 3.00 3.00 100.00 Ushio HQI 2.43 2.43 133.41 59.98Hz 339 118 Ushio ARO 2.94 4.64 125.43 77.95 249 119 Ushio eballast 1.80 1.59 123.04 86.68 243 119 Ushio IceCap 2.87 4.40 127.78 73.43 254 119 Ushio CV 1.84 1.62 125.39 72.84 254 121 Ushio ReefFanatic 2.62 3.20 116 44.06 246 119 Ushio EVC 2.10 2.42 132.20 41.98 246 120 Ushio Standard 2.11 2.11 129.34 59.98Hz 273 118

The Meat of it All: Testing the Lamps



Table 5 below represents the main thrust of the testing that was done. Each lamp was tested on the ballasts available to me at the time. I was asked to return the CoralVue ballast a few months after testing, so fewer lamps are shown on that ballast than on the others. I received quite a few different lamps after returning this ballast to the manufacturer. The measurements for all of the ballast/lamp combos tested are shown below. PAR is the reading from the Apogee sensor after 20 minutes of lamp illumination. The columns marked "Watts" and "Amps" represent the power drawn by the ballast from the wall's electrical socket after being passed through the voltage regulator. Generally speaking, ballasts need to produce an initially high current pulse to ignite the lamp, and in some cases this shows up as a high amperage draw that is captured under "Max Amps."

This series of charts demonstrate in PAR the amount of light available for photosynthesis. In general, we are looking for higher PAR values. The data are sorted by PAR value ranking.

Table 5

Legend:

AB13K = Aqualine Buske (AB) 13000K, (also labeled 10000K in some stores, but they are the same lamp), AQ14K = Aquaconnect 14K, BL10K = Blue Line 10000K (also called 10K+), BLSW = Blue Line Super White MH, CV10K = Coralvue 10000K, CV15K = Coralvue 15000K, CV20K = Coralvue 20000K, EVC10K = EVC Technologies 10000K, HM14K = Hamilton 14000K, Iwasaki = Iwasaki 6500K MH, PFO13K = PFO 13000K, Radium - Radium also called Radium 20000K, SBURST12K = Sunburst 12000K, SUN10K= Sun Aquatics 10000K, SUN20K = Sun Aquatics 20000k, SUN14K = Sun Aquatics 14000K, Ushio = Ushio 10000K, XM10K = XM10000K MH, XM20K = XM20000K MH

PAR values as an average.

A graph showing the average PAR value for each lamp from all the ballasts.

Bulb Appearance



The picture on the left is with actinics off. The picture in

the middle is with two 140-watt URI VHO actinics on.

AB13K : Aqualine Buske 13000K



AQ14K : AquaConnect 14000K



BL10K : Blueline 10000K



BLSW: Blueline Super White



CV10K: CoralVue 10000K



CV12K: CoralVue 12000K



CV15K: CoralVue 15000K



CV20K: CoralVue 20000K



EVC10K : EVC 10000K



HM14K: Hamilton 14000K



Iwasaki: Iwasaki 6500K



PFO 13K: PFO 13000K



Radium: Radium 20000K



SBURST12K: Sunburst 12000K



SUN10K: Sun Aquatics 10000K



SUN14K: Sun Aquatics 14000K



SUN20K: Sun Aquatics 20000K



Ushio: Ushio 10000K



XM10K: XM 10000K



XM20K: XM 20000K

Conclusions



When reading through all these data, the first thing to become apparent is that they are voluminous. Because of this, we need to have a goal in mind when viewing the data. The information can mean different things to different people. Looking at the data to simply find the best lamp will not yield good results. Rather, think long and hard about what you are keeping, what color lamp you enjoy, and what kind of ballast you are looking for.

In my case, I did change my lighting system after doing these tests. After starting the testing, I wanted to find a lamp/ballast combination that put out as much PAR as the Ushio/HQI ballast combination I had been using. Finally, I settled on the combination of the XM10K lamp and the Icecap electronic ballast. The Ushio on an HQI ballast still puts out about 15% more PAR than the XM10K running on an Icecap, but I felt that it was close enough. After making the switch my colors and growth were just about the same as before. The main differences are less heat produced and less electricity consumed.

Someone else's goal might be different, but it will make your life much easier if you have an idea of what you are trying to achieve when interpreting the data.

Acknowledgements



I would like to thank PFO Lighting, DIY Reef, Premium Aquatics, HelloLights, Ocean Encounters, Icecap, Champion Lighting, Sun Aquatics, Sanjay Joshi and all the hobbyists who lent me lamps and let me ask them questions about how to do these tests. Without all of you, I never would have been able to gather this information and pass it on.