Lighting

Last update: December 31, 2001
4765


Lighting is one of the most discussed and most confusing issues with planted aquariums. Everyone wants to know "What's the best light for plants?" This question seems to get the most varied answers simply because "best" can be defined in so many ways. Are you concerned about cost? Trying to optimize intensity? Looking for the best spectrum? Do you desire a "natural" appearance? Do you want to take prize winning photos? Are energy costs critical?  Is the initial expense a stumbling block? Do you have a closed hood or open top?  How deep is your tank? Do you want metal halide or fluorescent? 

<sigh>

Note: In case you get bored before you get to the end of this page, I would like to recommend Aquarium Hobbyist Supply as a most excellent source of compact fluorescent lighting kits and supplies. The owner, Kim, has gone out of his way to develop a superb series of lighting kits to suit any need. If you are retrofitting a standard canopy or building a custom hood, AH Supply has what you need. Joe Bob sez, "Two thumbs up!"


Lighting Terms
Recommendations
Measured Bulb Data - Part 1 (Color Temperature and Relative Intensity)
Measured Bulb Data - Part 2 (Relative Intensity)
Measured Bulb Data - Part 3 (Inverse Square Law ... NOT!)
Do-It-Yourself Hood
PennPlax Bulb Data
Common Bulb Data


Lighting Terms 

Before we discuss our favorite lights, let's look at some terms that are useful for lighting discussions.

Recommendations

Since there is so much information on the Internet about the "best" bulbs as seen by various authors, I will only describe the bulbs we like and why.

Fluorescent

We are primarily interested in the most intensity we can get in the space we have available and are also interested in the best color rendering possible, both for general appearance and for photography. Our two 100 gallon tanks (60"x18"x22" high) use four 40 watt fluorescent bulbs; two Triton and two PennPlax Ultra Tri-Lux. Both these bulbs are "tri-phosphor" bulbs, meaning they use three types phosphors rather than the usual two to produce a fuller spectrum. The third phosphor is a rare earth that accounts for the higher price. The Ultra Tri-Lux has a strong green component which accounts for its extra intensity.

Many aquarists believe that only red and blue light is needed for photosynthesis. This is true for algaes; this "fact" comes from older studies of photosynthesis in algae. However, higher plants have evolved to use many wavelenths of light and the green wavelengths are not wasted. Also, the stronger green component also helps bring out the natural green color in plants.

With these four bulbs about 3" from the surface in our hoods, we achieve around 13,000 lux at the surface. This has proven to be suffucient light for almost any plant we've tried.

The Triton bulb has a color temperature of around 8300K and the Ultra Tri-Lux has a temperature of around 6500K. The combination seems to match well with normal "daylight" film, even though the temperature seems too high. I suspect that the water acts as enough of a filter to balance the colors fairly well. All the photos in this site were taken with only the aquarium lights and regular print film.

Metal Halide

Our 120 gallon tank (48"x24"x24" high) uses two 175 watt 5500K metal halide bulbs. These are in a hood suspended 14" above the surface of an open top tank. Even though the two metal halide bulbs have much more intensity than four fluorescent bulbs, less of the light gets to the surface due to a poorer reflector and a greater distance from the water.

The 5500K Daylight bulbs are more expensive than standard 4300K bulbs, but the appearance of the tank is much nicer. The 4300K bulbs give a very yellow color to the plants, even though they will grow as well.

The 5500K bulbs also work very well with regular daylight film. We have the hood suspended from the ceiling with decorative swag chain and can lower the lights close to the surface for photography.

The one downside of metal halide lights is they don't bring out the color of red plants very well.


Measured Bulb Data

I made some intensity and color temperature measurements on a bunch of fluorescent and metal halide bulbs. My goal was to determine the relative brightness of various bulbs (to check out the claims of the vendors) and to get a feel for the color temperature of the bulbs. A secondary goal was to determine the effects of age on both color temperature and brightness.

To measure intensity, I used a lux meter offered by Marine Invertebrates, Inc. This is advertised in FAMA and costs about $100. I'm not sure about its absolute accuracy, but, being digital, its resolution is quite good. The instructions claim an accuracy of +/- 5 lux and it seems very repeatable. I'm also not sure about how color temperature affects its accuracy. Its response curve peaks at about 600 nm, so there is probably some effect.

To measure color temperature, I rented a Minolta Color Meter II from a photographic supply store in Denver. It's primary use is to determine the correction filters required to balance a specific film for a specific light source, but it also indicates color temperature in degrees Kelvin. I'm not sure of its absolute accuracy (and I did see some strange results with metal halide lights), so take the numbers with a grain of salt. This is a neat instrument that sells for about $700, so I feel that numbers aren't too far off for the fluorescent bulbs. Minolta also makes a different meter for "scientific and industrial colorimetery", but it's not available for rental locally.

BTW, I tried to call the Minolta Customer Service Department to determine the validity of my measurements, but the "representative was busy and his voice-mail was full", so I couldn't leave a message.

This posting is the raw data I collected. I have not as yet drawn any conclusions aside from obvious things like Penn-Plax Ultra TriLux bulbs are brighter than Triton bulbs and they have a color temperature closer to sunlight (whether or not that is good, I'm not saying).

Light Fixture Effects

To determine if the light fixture and ballast affected the temperature and intensity, 2 new 40 W Cool White bulbs (2 for $2.49) were tested in two fixtures. The readings were taken 8" from the bulbs, centered over the middle of the fixture.

An "electronic" shop light ($15.99 at Ace hardware) with a small coil/ capacitor ballast circuit produced 5000 K and 5500 Lux. This is an "energy saving" type fixture. My experience indicates this type of fixture is hard on bulbs such as Tritons and shortens their life.

As a side note, the October '92 Consumer Reports tested various types of energy saving light bulbs including compact fluorescent bulbs with electronic and magnetic ballasts. They found that a large number of the bulbs with an electronic ballast had premature failures.

A "standard" Sears shop light with a normal magnetic ballast produced 5300 K and 6650 Lux. The same fixture with aluminum foil behind the bulbs produced 5300 K and 7900 Lux. Also with this setup, the color temperature ranged from 5200 K to 5500 K when the distance from the bulb varied from 3" to 24".

I also tried to check the lights in a Coralife metal halide and fluorescent fixture to see if an "expensive" ballast and polished reflector did anything, but the bulb spacing was very different giving readings which could not be meaningfully compared to the first three.

Conclusions:

Color Temperature (single bulbs)

I had hoped to determine color temperature and aging effects of metal halide bulbs, but the temperature meter responded very strangely to most of the bulbs I tested, giving readings of 9000 K to 14000 K depending on the distance from the bulb. One older, 1000 W MH bulb read 6200 K, but I don't have much faith in that number. By the way, an actinic bulb caused an "overrange" reading (above 40000K).

The local fish store allowed me to check some of the bulbs in the store. Most of the bulbs are about 1 year old. I was surprised at the temperature range of the 40 W Power-Glo bulbs; possibly caused by differing age or fixture differences or just bad quality control - I don't know. I believe the higher K temperature indicates more blue, which shows up some fish colors better.

20w Ultra TriLux     5200 K   new      (in a cheapie hood)
Phillips UltraLume   5800 K   6 months
Artic Brite          6000 K   1 year
Power-Glo            7200 K   
  "    "             7850 K   
  "    "             8700 K
  "    "             8700 K                      
  "    "             9350 K
  "    "             9800 K
A local lighting store has a light bulb comparison center with various commercial bulbs. The age of the bulbs was unknown. Unfortunately, the store was remodeling and some of the display was not working, so I didn't get a chance to try a Chroma 75. 
Warm White Delux     3460 K
Warm White           3630 K   
Regal White          3640 K   
Natural              3900 K
Spectra 35           3930 K
Spectra 30           3930 K
Chroma 50            4600 K   
Cool White           5000 K
Cool White           5150 K   
Daylight             7500 K

We have quite a few bulbs of various ages on hand. Each was tested in the Sears shop light. The second bulb in the fixture was covered with a piece of cardbard so it would not affect the readings. The age of the the bulb is indicated, if it was known. All readings are 8" from the bulb.

Agro Lite            3590 K
Wide Spectrum        3900 K
Advantage X          5300 K          5100 K in electronic fixture
Artic Brite          5850 K    new   5900 K in electronic fixture
  "    "             5700 K    
Ultra TriLux         6750 K    new
  "     "            6350 K          6050 K in electronic fixture
  "     "            6150 K
  "     "            6150 K
Triton               8150 K    new
  "                  8400 K    new
  "                  7550 K    300 hours
  "                  7550 K
  "                  7350 K    4800 hours

Color Temperature (combinations)

Combinations of bulbs in use on our various planted aquariums were tested. The average age of the bulbs is about 6 months.

1 Power-Glo, 
1 Ultra TriLux       6550K   

1 Triton,            from 
1 GE Wide Spectrum,   6000 K   
1 Triton,              to 6300 K
1 Ultra TriLux          to 6500 K 

1 Ultra TriLux,      from 
1 Ultra Trilux,       6150 K 
1 Triton,              to 6050 K
1 Ultra Lume            to 5900 K

1 Artic Brite,
1 Ultra TriLux       6400 K

Intensity (single fluorescent bulbs)

From the local fish store (meter was 4" from the bulbs except for the metal halide bulb):

1000 W Metal Halide, 12" from fixture   69,000 Lux
2 Power-Glo bulbs,                      11,000 Lux
1 Power-Glo, 1 Ultra TriLux              8,200 Lux
1 Power-Glo, bad fixture                 2,400 Lux

From the local lighting store (meter was 4" from the bulbs):

Regal White          3300 Lux 
Chroma 50            3500 Lux 
Warm White           4600 Lux 
Cool White           5000 Lux

Our bulb stock (meter was 8" - twice as far - from the bulb):

Wide Spectrum        2400 Lux
Artic Brite          3750 Lux  new   2780 Lux in electronic fixture
  "    "             3200 Lux  
Advantage X          4200 Lux        3370 Lux in electronic fixture
Triton               3890 Lux  new
  "                  3820 Lux  new
  "                  3730 Lux  300 hours
  "                  3610 Lux
  "                  3300 Lux  4800 hours
Ultra TriLux         5000 Lux  new
  "     "            4720 Lux        3520 Lux in electronic fixture
  "     "            4580 Lux
  "     "            4480 Lux

Intensity (single 5500 K metal halide bulbs)

We have had our dual 175W metal halide fixture in use for over 1 year and have tracked the intensity of 3 of the 5 bulbs in use over that period. The bulbs are on for 10 hours per day.

Directly below the bulb at the acrylic shield:

Bulb 1:  78,000        90 to 270 days
         72,000        320 days
         57,000        360 days

Bulb 2: 126,000        10 minutes
        110,000        4 hours
        102,000        2 days
         94,500        4 days
         90,000        13 days
         90,000        21 days
         86,500        62 days
         82,000        110 days
         72,000        285 days
         60,000        315 days

At the water surface, 13" from the bulb:

Bulb 2:   9,900 Lux    1 year old; replaced at this point

Bulb 3:  19,900 Lux    after 2 hours
         17,600        1 day (12 hours)
         17,100        2 days (22 hours)
         16,900        3 days
         16,400        4 days
         15,700        6 days
         15,700       16 days

I was very surprised at the rapid initial drop off of intensity from the MH bulbs; I had expected a linear drop for most of the lifetime. The data indicates that MH bulbs should be changed once a year if you have intensity sensitive applications.


More Measured Bulb Data

The following intensity measurements were made on a number of bulbs that we have, both new and used. All bulbs are standard 48" 40 watt fluorescent bulbs. The measuring setup was different than the setup used above, so these values are relative only to other values in this section.

The bulbs were put in a Sears magnetic ballast shop light with black cloth covering the second bulb and the reflector so the readings are direct light only. The measurements were taken 3" from the bulb in the middle of the bulb. A piece of PVC tubing 2.5" in diameter was used to support the lux meter sensor to get fairly repeatable readings. Each bulb was allowed to warm up for 5 minutes before a reading was taken.

These numbers are for comparison only. Because of the test conditions, they cannot be used to calculate any quantitative data.

Bulb       Age       Lux
------     --------  ---------
TriLux     new       7800
  "        new       7600
  "        1800 hrs  7100
  "        1800 hrs  6800
  "        3600 hrs  6800
  "        ???       6800
  "        ???       6700

AX50       ???       5800       

Triton     new       6100
  "        new       5700
  "        ???       5600
  "        1800 hrs  5400
  "        1800 hrs  5000
  "        1800 hrs  4900
  "        3600 hrs  5300

Daylight   1800 hrs  5400

WarmWhite  ???       5000

BioLume    1800 hrs  4600

Chroma50   1800 hrs  4100
  "        1800 hrs  3800

VitaLite   ???       3900


TriLux     = Penn-Plax Ultra TriLux
AX50       = Phillips AX50 Advantage X
Triton     = Triton
Daylight   = GE Daylight
WarmWhite  = GE Warm White
BioLume    = Rainbow Lifeguard Biolume with internal reflector
Chroma50   = GE Chroma 50
VitaLite   = Vita Lite


Even More Measured Bulb Data

The following data was collected to settle a discussion on rec.aquaria about the "inverse square law".

Dustin Lee Laurence (laurence@cco.caltech.edu) wrote:
>
> Grant.Gussie@phys.utas.edu.au (Grant Gussie) writes:
> >The famous inverse square law applies ONLY to a point source of light that
>
> In fact, the 1/r intensity rule for line sources is not terribly
> relevant either as far as fluorescent lit reefs is concerned.  1/r^2
> is more than accurate enough for considering metal halide lighting,
> which is for these purposes a small number of point sources which can
> be superimposed incoherently. 

Here's what I measured last night. These were quick and dirty measurements made after consuming a lovely cocktail and as such, probably don't qualify for the Journal of the Society of Lighting Engineers. But they should be good enough to add fuel to the fire :-). I didn't get around to the MH light yet, maybe tonight.

Executive summary:

Light Intensity in Air

                                    Distance from center of bulb (cm)
                                      10       20      40     80    120
------------------------------------------------------------------------
1. Sears shoplight; 1 Triton,       10,800    5,300   2,400   940   530 
   1 Coralife TriChromatic

1.5 measured at end of fixture       6,900    3,400   1,600   780   450

2. Sears shoplight, 1 Triton,       15,050    8,000   3,600  1,520  810
   1 Ultra Trilux

3. Sears shoplight, 1 Triton,       13,500    7,200   3,100  1,370  780
   1 Ultra Trilux

4. Triton Enhancer, 1 Triton,       13,300    8,400   4,100  1,630  830
   1 Ultra Trilux

Notes:
1. All fixtures use magnetic ballasts.
2. All measurements made at center of fixture (except 1.5).
3. Bulbs are various ages.
4. Intensity values are lux (lumens per square meter).
5. Sears shoplight reflector is "w" shaped; Triton Enhancer is
   "sort of" hemispherical.  Enhancer seems to help a little at longer
   distances. 

Light Intesity in Water

                                  Distance below surface of water (cm)
                                       0       10      20     30     40
------------------------------------------------------------------------
1. Bulb and fixture from (3)        16,000    8,800   7,700  6,500  5,100

Notes:
1. Measurements made in a 29T gallon tank with water only. 
2. Fixture positioned at back of tank and overhung the sides by 9".
3. Measurements made below center of bulb. 
4. Bulb centerline was 5 cm above water surface.
----------------------------------------------------------------------------

The intensity in water was surpising at first. From 0 to 10 cm, the intensity dropped by half. Below that, the intensity dropped much less and linearly with distance. I speculate that reflections from the sides of the glass were augmenting the intensity at lower depths and cannot be depended on in a real setup with plants and all. When I get the 120 gallon tank setup, I will repeat these measurements. It is 24" wide and 48" long, which should reduce the reflections.


Building a Do-It-Yourself Hood

The following describes the hood I made myself for our 85 gallon tank. I have also had two more professionaly made out of oak (for better appearance). The goals of the hood design were:

The hood is designed for an 85 or 100 gallon acrylic tank: 60" long by 18" wide (front to back). The basic design is a box, open at the bottom and split across the top with a piano hinge holding the two halves together. Two shop light fixtures are attached to the inside top of the hood. The height of the hood is enough to allow the bottom of the light fixtures to move over the tops of any external equipment. The back is partially open to allow it to slide backwards over the equipment and to provide ventilation for the lights. The hood fits over the rim of the tank and rests on some 1/2" sq recessed wood strips on the side of the hood. If you have a 48" by 12" tank (55 gallon), you will need to make adjustments for the length and width of the light fixtures.

                           front          hinge         back
                              _____________ ______________
       side view:             |     MMM   -o-   MMM      |
                              |   /=====\  :  /=====\    :
                              |  / O   O \ : / O   O \   :
                              |            :             :
                wood strips-> |n___________:____________n:
                               |                        |                 
                               |    tank                |                 
                               |                        |                 

To feed the fish or do minor maintenance, the front half of the hood is pivoted upwards and allowed to rest on the rear half:

                                           ...............
                                           :            n|
                                           :\         /  |
                                           : \ O   O /   |
                                           :  \=====/    |
                                           :____WWW______|
                                           o______________
       side view:                          :    MMM      |
                                           :  /=====\    :
                                           : / O   O \   :
                                           :             :
                               _________________________n:
                               |                        |                 
                               |    tank                |                 
                               |                        |                 

To do cleaning and heavy maintenance, the front part is raised like the previous picture and the whole assembly is slid back 4 or 5 inches until it hits the wall behind the tank. The first hood had some push-button switches on the side to turn on the front and rear lights independently (turn off the front half so you aren't blinded when you raise the front!). On the other two, I mounted the switches inside, out of sight (you are only temporarily blinded when you raise the hood to get to the switch!).

To build the hood, I made two frames of 1/2" square pine strips (kind of a "wire frame" model of each half of the hood). I then nailed and glued 1/4" tempered (waterproof) Masonite on the front (or back), sides and top of the frames. I didn't overlap the corners of the Masonite, so there was a 1/4" "notch" all the way around the top and sides. I obtained some 1/4" square basswood from the local hobby shop and glued this in the notch. Using a "Surform" tool, I rounded the bassword to give a nice edge (It would be hard to round off the Masonite). A little Plastic wood or spackling filled in any imperfections, so the hood looks like a one piece unit. The only "precision" woodworking required is to cut the Masonite nice and square. The frame simply serves as a way to connect the Masonite pieces and act as a support rails for the hood; all the strength is in the Masonite.

                                       Masonite top
             1/4" basswood       ___________________________
             goes here ------>  _|__________________________| O <- 48" Piano
                               | |   |                  |   || |     hinge
                 Masonite ->   | |   |__________________|   || |
                  front        | |   |                  |   |
                               | |   |                  |   |
                               | |   |                  | o---- 1/2" pine
                               | |   |    Masonite      |   |   frame
                               | |   |      side        |   |
                               | |   |                  |   |
                               | |   |                  |   |
                               | |   |__________________|   |  frame rests on
                               | |   |                  |   |  top of tank 
      front and sides extend   | |___|__________________|___|  _______________
      below frame to hide      | |                          |  |
      top edge of tank         |_|__________________________|  |   tank

I painted the hood white and sealed the inside with Marine varnish. The smooth, seamless white hood gives the tank a very modern look. I guess you could get veneer and cover the outside to make it look like wood. I have been very happy with the hood; it makes access to the tank very easy and it looks good. There has been no warpage of any kind (over two years).


Manufacturer's Data for Penn Plax Aquarium Bulbs

     Lumens (40 watt)

FL-40  "Aquarilux"       900
FS-40  "Sea-Lux"        1570
NL-40  "Natura-Lux"     2450
FT-40  "Tri-Lux"        2480
FUT-40 "Ultra Tri-Lux"  3350

     Wavelengths     cl wht   FL-40   FS-40   NL-40   FT-40   FUT-40
---------------------------------------------------------------------
u-v     than 380 nm |  1.7% |  1.7% |  1.5% |  1.8% |  0.5% |  0.6% |
violet   380-430 nm |  7.6  |  8.6  | 11.2  |  9.8  |  3.1  |  4.1  |
blue     430-490 nm | 20.8  | 24.6  | 20.6  | 21.4  | 38.4  | 29.8  |
green    490-560 nm | 24.6  | 13.2  | 19.1  | 25.5  | 21.2  | 34.1  |
yellow   560-590 nm | 18.3  |  4.1  |  8.1  | 13.2  |  3.6  |  4.5  |
orange   590-630 nm | 17.7  |  7.9  | 12.3  | 12.6  | 23.5  | 20.1  |
red      630-700 nm |  8.5  | 36.7  | 22.7  | 11.7  |  7.3  |  5.0  |
i-r      700-800 nm |  0.8  |  3.2  |  4.5  |  4.0  |  2.4  |  1.8  |


     Wavelengths     cl wht   FL-40   FS-40   NL-40   FT-40   FUT-40
---------------------------------------------------------------------
u-v     than 380 nm |   52  |   15  |   24  |   44  |   12  |   20  |
violet   380-430 nm |  232  |   77  |  176  |  240  |   77  |  137  |
blue     430-490 nm |  634  |  221  |  323  |  524  |  952  |  998  |
green    490-560 nm |  750  |  119  |  300  |  625  |  526  | 1142  |
yellow   560-590 nm |  558  |   37  |  127  |  323  |   89  |  151  |
orange   590-630 nm |  540  |   71  |  193  |  309  |  583  |  673  |
red      630-700 nm |  259  |  330  |  356  |  287  |  181  |  168  |
i-r      700-800 nm |   24  |   29  |   71  |   98  |   60  |   60  |



Data for Common Fluorescent Bulbs

Here are some manufacturer's specifications for various commonly available 40 watt fluorescent bulbs (sorted by intensity):

   Manuf      Brand Name    Mfg Number      Temp  CRI  Lumens
   ------     ------------- -----------     ----  ---  -----
   GE         StayBright    F40SXL/SP41     4100K  70   3400          
   PennPlax   Ultra TriLux  FUT-48          6500K   ?   3350          
   Philips    Advantage     F40AX50         5000K  80   3300
   GE         Warm White    F40WW           3000K  52   3150          
   GE         Shoplight     F40SHOP         4150K  62   3100          
   GE         Cool White    F40CW           4150K  62   3050          
   Philips    Ultralume     F40/50U         5000K  85   2950
   GE         Daylight      F40D            6250K  75   2550          
   PennPlax   Tri-Lux       FT-48               ?   ?   2480          
   Philips    Daylight      F40D            6500K  79   2250
   GE         Dlx Cool Wht  F40CWX          4175K  89   2250          
   GE         Chroma 50     F40/C50         5000K  90   2250          
   GE         Soft White    F40SW           3025K  52   2200          
   GE         Dlx Warm Wht  F40WWX          3025K  77   2200          
   GE         Chroma 75     F40/C75         7500K  92   1950          
   Philips    Corortone     F40C50          5000K  92   1915
   GE         Plant & Aquar F40PL/AQ        3050K  90   1900          
   Philips    Colortone     F40C75          7500K  95   1720
   PennPlax   Aquarilux     FL-48               ?   ?    900           
   GE         "Gro & Sho"   F40PL           6750K   ?    800