Following is an excerpt from
"Lighting Choices for the Marine
Aquarium," by Gregory Schiemer,
which appeared in the March 2000 issue of Aquarium
Fish Magazine. To see the entire article,
JUMP TO SECTION:
Choices for the Marine Aquarium
The working title of this article
was "Lighting Choices for the Reef Aquarium."
I then got to thinking that all tropical marine
aquariums, whether they include live corals or
not, should be constructed and maintained as reef
aquariums. The word "biotope" has become
a popular term lately in the aquarium hobby, and
with good reason. Animals do best and look their
best when maintained in a captive environment
most similar to their natural environment. The
majority of tropical marine fish come from areas
of coral reefs, so their captive habitat should
be set up to mimic that environment. If
you were keeping rift lake cichlids you would
assemble an aquarium that included rocky outcroppings
and alkaline water. Amazonian angelfish look best
in a tall tank that includes swordplants, replicas
of submerged tree roots and driftwood. So, when
it comes to keeping coral reef fish, the aquarium
should contain - at a minimum - structures of
calcareous rocks (live reef rock is best) and
possibly coral sand as a substrate. The water
quality should be maintained within natural reef
The decisions regarding lighting
should be based upon the same criteria. Lighting
is an important aspect of the natural environment
of fish. I've seen it written that lighting is
unimportant if an aquarist intends to keep only
fish. It's often recommended to use just enough
light to view the fish. Based upon my experiences,
this is not only unnatural (most tropical marine
fish come from areas of clear water and bright
sunlight), but also unhealthy. Insufficient light
can be a stress factor and has been implicated
in "head and lateral line erosion."
The physical dimensions of the aquarium and the
nature of its inhabitants should dictate the type
and quantity of lighting.
TYPES OF LIGHTING
Marine aquarists are faced with a bewildering
array of choices when it comes to lighting. Before
we get into choosing the most appropriate lighting
scheme for your aquarium, let's take a look at
what's available in lighting and the characteristics
of each type.
Power compact (PC) lamps are the latest addition
to the aquarium lighting market. They are fluorescent
lamps that can best be described as standard fluorescent
tubes that are folded back on themselves to form
a tight "U" shape. The result is a lamp
with a relatively small footprint but with higher
output compared to similarly sized standard fluorescent
tubes. Also, unlike traditional fluorescent
tubes, PCs are single ended. They have two or
four pins at one end of the lamp and fit into
a unique lamp holder.
PC lamps require special ballasts.
These ballasts can be traditional electromagnetic
or the newer (and more efficient) fully electronic
variety. Most of the better fixtures on the market
use small electronic ballasts. For a list of the
most popular PC lamps available in the hobby,
see Table I below.
PC lamps and fixtures are sold
by many companies in numerous forms and configurations.
They were first popularized for the aquarium hobby
by Custom Sealife, but are now available from
numerous manufacturers. Some of the prominent
manufacturers and their offerings include:
- Aquarium Systems - 55-watt
PC striplights in one and two tube configurations.
- Custom Sealife - Replacement
lamps, full hoods, retrofits, and combination
metal halide/PC hoods and retrofits.
- Hamilton Technology Corporation
- Full hoods, retrofits and combination metal
halide/PC hoods and retrofits.
- IceCap, Inc. - Replacement
and do-it-yourself electronic ballasts for 28-,
55- and 96-watt PC lamps.
- Osram - 55-watt PC lamps.
- Panasonic - 9-, 13-,
55- and 96-watt PC replacement lamps.
- Perfecto - 55-watt PC
striplights in one and two bulb configurations.
Some of the benefits of PC lamps include:
are relatively cool compared to metal halide
are compact in size
are energy efficient, compared to standard fluorescent
and very high output fluorescent tubes run on
- The lamps and parts are generally
available within the aquarium trade.
Some of the downsides of PC lamps include:
lamps are relatively expensive compared to standard
and very high output fluorescent tubes
useful life is not appreciably longer than standard
and very high output tubes, especially if they
are used in conjunction with electromagnetic
sizes, color temperatures and wattages compared
to standard and very high output fluorescent
- Limited availability.
PC lamps and parts can be hard to find outside
the aquarium industry.
For a thorough discussion of
PC lighting, including a wealth of do-it-yourself
information, you can refer to the article by Sanjay
Joshi in the April 1999 issue of Aquarium Frontiers
HIGH OUTPUT AND HIGH OUTPUT FLUORESCENTS
Very high output (VHO) and high output
(HO) fluorescent tubes are similar in size and
appearance to standard regular output fluorescents,
but use a heavier filament that enables them to
be driven at much higher wattages. The result
is, of course, more light output in the same amount
of space. These lamps were initially popularized
in the aquarium hobby back in the 1980s. They
were the first lights used over reef aquariums
that truly enabled aquarists to maintain some
of the photosynthetic corals in captivity for
the first time. They are still very popular today
used alone or in combination with metal halide
bulbs over reef aquariums.
HO lamps differ from VHO lamps
in that they use less wattage and produce less
output. They fall between regular output and VHO
lamps. HO lamps are rarely used or offered for
sale today for the aquarium hobby. VHO lamps can
be driven by conventional "tar" ballasts
(rated for VHO lamps), but are much more useful
and efficient when driven by electronic ballasts
- VHO fluorescent lamps are
offered in many sizes and wattages. Some of
the more popular types used by aquarists are
listed in Table II.
- VHO fluorescent lamps and
lighting fixtures are sold by many companies
in many forms and configurations. Some of these
- Coralife (Energy Savers Unlimited,
Inc.) - Fixtures in combination with metal halide
lamps, retrofits in combination with metal halide
lamps and replacement lamps (10,000 K).
- Duro-Lite Lamps Inc./Duro-test
Corp. - Vita-Lite VHO daylight and actinic lamps.
- Hamilton Technology Corp.
- VHO fixtures, combinations with metal halide
lamps, retrofits and replacement lamps.
- IceCap, Inc. - VHO electronic
ballasts (IceCap), hoods and retrofits.
- Ultraviolet Resources International
(URI) - Replacement fluorescent lamps.
- Ultralife: Electronic VHO
ballasts (Sun Seeker) and replacement lamps.
- Voltarc - Replacement lamps.
Some of the advantages of VHO lighting compared
to other forms of aquarium lighting include:
- There is a large choice of
lamp styles and sizes to fit every possible
- VHO lamps can be very efficient
and long-lasting (up to 12 months) when used
with electronic ballasts
- VHO lamps are relatively inexpensive
on a dollar per watt basis compared to metal
halide bulbs and PC lamps
- VHO bulbs, ballasts and associated
hardware are available from many sources.
Some disadvantages of VHO lighting include
- The tubes need to be changed
frequently (every four months), and there is
a quick drop-off in output when used on conventional
- Conventional ballasts get
- SOME VHO electronic ballasts
can be finicky (e.g., electrical interference
problems, sudden shut-offs, unexplained breaker
trips, blown fuses)
- VHO electronic ballasts
HALIDE AND HQI BULBS
Metal halide and HQI bulbs emit a point source
of light, unlike fluorescent lamps in which the
light output is spread over a tube. Metal halide
bulbs have single-ended screw bases in both standard
and "mogul" sizes. HQI-type metal halide
bulbs have pins on both ends of the bulb that
"snap" into a holder. HQI bulbs must
be used in conjunction with a glass ultraviolet
(UV) shield. Standard metal halide bulbs have
integral glass shrouds like standard incandescent
bulbs that allow them to be used unshielded. Both
metal halide and HQI bulbs operate on a range
of high-voltage ballasts. There are conventional
"core and coil" ballasts and newer electronic
ballasts. The ballast must be tailored to a specific
wattage bulb for it to operate properly.
Coralife (Energy Savers Unlimited,
Inc.) first popularized the use of metal halide
bulbs as an alternative source for reef aquariums
back in the early 1990s. They introduced the first
daylight color temperature metal halide bulbs
(4300 Kelvin [K] and later 5500 and 6500 K bulbs)
for aquarists. Originally only 175-watt bulbs
were available to hobbyists; today there are numerous
choices in metal halide lighting.
Some of the common wattages and
color temperatures include:
- 100-watt - 5500 K from Venture/Coralife
- 150-watt - 6500 K by Iwasaki,
10,000 K HQI from Red Sea and Aqualine-Buschke
- 175-watt - 6500 K by Coralife,
10,000 K from Coralife, Hamilton, and Aqualine-Buschke,
20,000 K from Coralife
- 250-watt - 5500 K by Coralife,
6500 K by Iwasaki, 10,000 K screw base from
Coralife, Hamilton and Red Sea, 10,000 K HQI
from Red Sea and Aqualine-Buschke, 20,000
K from Coralife
- 400-watt - 5500 K by Coralife,
6500 K from Iwasaki, 10,000 K from Coralife,
Aqualine-Buschke and "German," 20,000
K from Coralife, "German"
- 1000-watt - 5500 K by
Coralife, 10,000 K from Red Sea, Aqualine-Buschke
- Metal Halide fixtures and
bulbs are sold by many companies in many configurations.
Some manufacturers combine PC, VHO and regular
output fluorescents with metal halide bulbs.
The major manufacturers include: Coralife (Energy
Savers Unlimited, Inc.), Hamilton Technology
Corporation and Custom Sealife.
Metal halide lighting offers a number of benefits.
- There is a wide choice of
lamps, configurations and styles
- Parts and bulbs are readily
available at many places in and out of the aquarium
- It is an efficient source
- Metal halide bulbs are long
lasting. Some bulbs can be kept in service in
excess of one year
- It is the only option that
features a point source of light, which is most
similar to the sun. The glitter lines created
by this type of lighting are natural and aesthetically
appealing as well
- Metal halide bulbs are the
best choice for obtaining high-intensity lighting
over a small space and to satisfy the needs
of certain reef crest small-polyped scleractinian
Some of the drawbacks to metal halide lighting
- Metal halide fixtures and
bulbs are expensive
- The ongoing costs of electrical
use and bulb replacement are very high
- Metal halide bulbs get very
hot and must be ventilated. Even with ventilation
they tend to raise the temperature of the aquarium
by a few degrees
- Some electronic ballasts designed
for metal halide bulbs can be finicky
- The large external ballast
boxes and wiring associated with these bulbs
are difficult to hide and conventional (non-electronic)
ballast boxes also get very hot
- There is some incompatibility
of ballasts, even with bulbs of the same wattage.
REGULAR OUTPUT FLUORESCENTS
I've included standard fluorescent lighting in
this treatise because they are still the most
popular and widespread of choices for aquarium
lighting. Some of the newer T-8 fluorescent tubes
and fixtures, when combined with electronic ballasts,
make attractive and efficient alternatives for
marine aquarists interested in maintaining a fish-only
reef aquarium. Their compact size and efficiency
rival that of PC lamps.
The strong points of regular output fluorescent
are available in a wide array of color temperatures
and replacement tubes are easily attainable
both in and out of the aquarium trade
are inexpensive and cool running
- They are useful as dawn/dusk
lighting when combined with metal halide bulbs.
They also have some weaknesses, which include:
are generally insufficient for use over reef
aquariums containing photosynthetic invertebrates
- They take up a lot of space
relative to their output. They require many
tubes over the length of the aquarium in order
to get sufficient light to maintain photosynthetic
There are no hard and fast rules when
it comes to choosing lighting for the marine reef
aquarium. I've seen successful reef tanks using
all the forms of lighting detailed in this article.
One common recommendation is to use between 3
and 5 watts of light per gallon over the typical
reef aquarium. This actually isn't a bad recommendation.
I would recommend using an absolute minimum of
3 watts of fluorescent lighting per gallon over
the typical fish-only reef aquarium.
When using fluorescent lighting
it is important to span the entire length of the
aquarium with lamps. For example, to light a 4-foot
long aquarium, you would use lamps totaling 48
inches in length. These can be single lamps or
a combination of shorter lamps.
At the other end of the spectrum,
I recommend a mix of metal halide and fluorescent
lighting totaling over 5 watts per gallon for
a reef aquarium dominated by SPS corals. If you
have an unusually shaped tank, you may need to
modify these recommendations. For example, I would
use a metal halide pendant light totaling 5 watts
per gallon to light a tall narrow tank such as
a hex-shaped aquarium, especially if I planned
to maintain photosynthetic invertebrates at the
bottom of the aquarium.
Bulbs and lamps can vary significantly
in terms of efficiency, longevity and aesthetics.
Choosing what's best for your aquarium can be
a daunting task. My suggestions are to read as
many independent reviews on lighting as possible,
such as this article and those that have appeared
in Aquarium Frontiers, and to look at other successful
reef aquariums. In this case a picture is truly
worth a thousand words. If you can see a successful
aquarium first-hand and the look appeals to you,
then you might want to emulate that lighting scheme.
Personally, I've had good long-term
experiences with the Iwasaki 6500 K series of
metal halide bulbs in the 250- and 400-watt sizes.
They are my bulbs of choice in those wattages.
I combine VHO lamps with these metal halide bulbs
to simulate dawn/dusk and to add a blue tinge
to an otherwise harsh white light.
The new 10,000 K 250-watt HQI
bulbs have been getting glowing reviews and are
worth considering as well. If they are similar
to the other 10,000K HQI bulbs originating from
Germany, they should offer a crisp blue-white
light and good long-term performance. The downside
to these is that they require a specialized ballast
to operate properly.
175-watt 10,000 K bulbs are my personal favorites
in the 175-watt metal halide group. They offer
a good compromise of aesthetics, efficiency and
I use 150-watt 10,000 K German
HQI bulbs over small reef aquariums and freshwater-planted
tanks with good success as well. The 10,000 K
HQI bulbs are relatively expensive and not widely
available, but the pleasing blue-white light and
long-life are appealing characteristics. Also,
because the HQI bulbs are physically smaller than
standard metal halide bulbs, they can be built
into small and fashionable fixtures.
When I choose to use fluorescent
lighting I prefer VHO lamps driven by IceCap electronic
ballasts. This is a cool-running and efficient
combination. As for the lamps themselves, I've
had the best experiences with the Ultraviolet
Resources, Inc. (URI) brand. URI lamps have been
consistent performers and are high quality. I've
used URI actinic, daylight and actinic/white lamps
with equally good results.
Regardless of the type of lighting you
choose, it's necessary to perform routine maintenance.
One aspect of maintenance is replacing lamps and
bulbs. It's important to develop a regular schedule.
Here are a few of my suggested
Regular output, PC and VHO
fluorescents can have useful lives in excess
of 12 months when run on electronic ballasts.
My suggestion is to replace them annually.
Regular output, PC and VHO
fluorescents that run on standard core and
coil ("tar") or electromagnetic
ballasts have a considerably shorter useful
life. In this case I suggest replacing regular
output and PC lamps every nine months and
VHO lamps every six months.
Metal halide bulbs are a
mixed bag because so much depends upon the
individual bulb or bulb/ballast combination.
The replacement schedule is also affected
by the adaptability of the animals (e.g.,
SPS corals and Tridacnid clams are generally
less forgiving of insufficient light). Some
of the work done by Sanjay Joshi and Richard
Harker suggests that the daylight metal halide
bulbs (e.g., Iwasaki 6500 K series) can be
used well in excess of one year, but the high-temperature
"blue" metal halides (10,000 K and
20,000 K German and Coralife) lose a significant
percentage of their useful output inside of
one year. My general suggestions are to replace
the high temperature metal halide bulbs every
nine months and the daylight bulbs annually.
You can get more detailed information on this
topic by referring to the following issues
of Aquarium Frontiers:
It's important to never replace
all the bulbs/lamps at one time. It could
shock photosynthetic animals. The stress of
this shock can lead to an expulsion of zooxanthellae
(symbiotic dinoflagellates) and ultimately
death. It's best to stagger the replacement
schedule so that bulbs and lamps are replaced
three months apart.
I can't overemphasize the
importance of keeping bulbs, lamps, reflectors,
shields, tank covers and tank braces clean
of salt and dust. When these are dirty they
can markedly reduce light output. The cleaning
of these items should be part of a weekly
Ballast boxes for all types
of lighting can get very hot and operate at
high voltage. It is essential that they are
kept clean and well ventilated. Saltwater
and salt dust are good conductors of electricity.
It is highly recommended that all ballasts
be plugged into ground fault circuit interrupter
(GFCI)-protected outlets. In the event of
a short, which can occur if water is splashed
onto a ballast box or lamp holder, the circuit
breaker will immediately trip. This will protect
both you and the electrical equipment. GFCI
breakers are required by many building codes
for areas where water has the potential to
When using any high-intensity
lighting in an enclosed hood it's imperative
that the enclosure be vented in some fashion.
Most prefabricated hoods for PC and metal
halide lighting come with one or more built-in
fans to dissipate heat. These fans should
be checked daily and cleaned monthly. If dust
is allowed to build up unchecked the fans
will eventually stop working.
As with all maintenance routines,
it's a good idea to keep a log. At a minimum
you keep track of the dates that bulbs are
replaced. I use small stickers with dates
indicating when the bulbs were put in service
and attach these directly to my fixtures.
It's one of the many aquarium-related uses
that I've found for my Brother P-Touch labeling
UPGRADES AND ACCESSORIES
One of the best investments you can make in your
lighting system is a good reflector. The
“reflectors” in many older fixtures were simply
created by painting the inside surfaces with flat
white paint. Over time this paint fades, discolors
Covering the inside of your light
hood with a new "specular" (mirrored)
aluminum reflector (e.g., Digital Ocean's Spider
Light) can increase light output dramatically.
Replacing a reflector is certainly within the
ability of even the most amateur of do-it-yourselfers.
For more information on the benefits of reflectors
see Richard Harker's article in Aquarium Frontiers:
Electronic ballasts are another
useful upgrade. Although they are costly, the
gain in efficiency and longevity of the lamps
will repay for the cost of the ballast in a relatively
short period of time. I personally would not operate
VHO fluorescent lamps without electronic ballasts.
I don't consider VHO lighting a viable alternative
when used with "tar" ballasts. Ballast
upgrades can also be a do-it-yourself project,
but I would suggest deferring to a qualified electrician
if you don't have the basic experience and skills
in working with electrical wiring.
One last useful device to consider
is a light timer. As important as light intensity
is, duration is equally critical for the health
and well being of all marine aquarium inhabitants.
It too is part of our attempt to simulate natural
conditions. I run VHO actinic fluorescent lamps
for a few hours before and after my main metal
halide lighting to simulate periods of dawn and
dusk. It's not necessary to mimic the actual local
times of dawn and dusk - simply keep the aquarium
on a regular schedule. Because I work during most
of the daylight hours, my main metal halide lighting
doesn't come on until late afternoon. By the time
I get home in the early evening my aquariums are
at the peak of the lighting cycle. I don't begin
the dusk phase until 10:30 p.m. The total photoperiod
is 13 hours. The peak lighting period is eight
There are many variations
of light timers sold in the aquarium marketplace,
but simple lamp timers that are available at all
home improvement and hardware stores work well
enough for most purposes. I suggest purchasing
the heavy-duty (rated 15 amps) timers that offer
a grounded receptacle.