 Aquarium Lighting
The Importance of Lighting
Most novice aquarists underestimate the importance of lighting on
their new fish environments. The average aquarium set-up contains one
all-purpose bulb which implies that special lighting is not necessary.
Lighting is of VITAL importance to the marine aquarist and a high
priority for tropical fish keepers if they wish to simulate a true
under-water environment that is both healthy and visually appealing.
Corals and invertebrates use lighting to regulate and assist in
digestion, feeding, reproduction and growth. Plant aquariums need
proper lighting in order for plants to thrive. A fish-only tank will
benefit from correct lighting with increased coloration, activity and
spawning.
Light Spectrum
The most obvious use of lights is to light the tank so that you can
see your fish. Light spectrum runs from violet on the short end (320
nanometers) to red on the long end (700 nanometers). Remember your
red, orange, yellow, green, blue, indigo, violet light spectrum? Below
are two light bulb spectrums represented visually by peaks and valleys
on a ROY G BIV scale.
The sun has 3 wavelengths: UVA, UVB, and UVC. UVA is the visible
wavelength of light and is responsible for the "physiological
well being" of fish. The 420nm blue (UVA) range is particularly
important to marine corals and invertebrates and also helps stimulate
feeding and breeding behavior in fish.
UVB is the non-visible wavelength of lighting. UVB is
the spectrum which gives humans a suntan. This is a critical component
for reptiles in that the 320nm range of violet (UVB) is needed for
many animals to assimilate calcium into their systems.
UVC is the wavelength used for Ultraviolet Sterilizers which
kill harmful bacteria. This wavelength is very dangerous to all
animals.
Different spectrums are required for different species who dwell in
different latitudes and at different water depths in their natural
environments.
Full Spectrum Light/CRI Rating
Full spectrum light is a light source that emits all of the
wavelengths of the visible spectrum in proportion to that of natural
sunlight. To give you the best color rendition (CRI rating) and bring
out the natural beauty of aquarium fish and plants in both freshwater
and marine tanks, choose a daylight lamp with a full spectrum of
visible light. A CRI as close to 100 (the CRI of natural sunlight) is
desirable for visual affect. Its spectrum graph would have higher
peaks in the middle of the spectrum with low ends.
Kelvin Rating
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 lower the content of blue light
waves, the lower the color temperature. During the day, the color
temperature of sunlight varies. It also changes at different depths
underwater as reds are filtered out more rapidly than blues.
Although blue spectrums penetrate deeper into water, species which
live fairly deep rarely see the red end of the spectrum because it is
filtered out by the water. They can actually be "bleached"
to colorless by a light that is too intense. A "K" or Kelvin
rating of 5000-5500 is a good estimate to simulate a noon sun in most
tropical environments.
Stimulate Spawning & Appetite
In freshwater aquariums, you may add tubes with UVA emissions
(higher in blues) and you will begin to stimulate feeding and mating
behavior in your fish.
Healthy Plants
To maximize the photobiological process in plants, add more red AND
blue spectrum, as plants require both red and blue enhancements. The
use of a floral bulb with a daylight bulb will give good visuals AND
healthy plants. (Remember, if you use plant-enhancing daylight with
added red and blue spectrums, you may also increase the undesirable
algae growth in your tank, so don't enhance these spectrums unless you
have adequate freshwater plants to battle for the algae nutrients)
Trichromatic bulbs are an excellent full spectrum daylight lamp and
provide maximum daylight simulation. They are very good for freshwater
tanks simulating 10-15 feet of water depth. This is best for visuals
as well as brightness. Some trichromataics are also high in blue UVA
emissions to stimulate feeding and breeding behavior.
Marine and reef tanks are VERY specific. A minimum of two
fluorescent light sources is almost always required, and even more
tubes is often beneficial.
Actinic Light
Actinic light promotes the growth of Zoaxanthellae algae, essential
for the growth and well-being of all photosynthetic corals and
invertebrates (not macro algae). However, Actinic and strong blue
spectrum lighting is visibly blue and will definitely need a full
spectrum bulb to help offset the color distortion.
If your reef or marine tank appears too blue, balance its visible
spectrum with a more intense daylight bulb or add another daylight
bulb to the group. 5,000K-6,000K is usually pretty good. However,
remember that macro algae can be a problem. Too much
"daylight" (with enhanced red spectrum) will promote plant
growth, and macro-algae responds similarly. A good rule of thumb is to
use one actinic lamp and one or two daylight lamps for each 30 gallons
of water.
50/50 Light
The 50/50 bulbs were developed specifically for marine and reef
tanks where the hobbyist wants the best of both worlds: healthy
invertebrates as well as visual appeal. If you can't decide, go for
one or two 50/50's.
Lighting Tips
The color spectrum of a lamp changes with age. Although it may
still look like visible light, the first wavelengths to go are the
blue and UVB/UVA spectrums not visible to the eye. If your lights are
not changed at least once per year (preferably every 6-8 months) you are
probably not getting the original spectrum of light for which the bulb
was rated, and your tank inhabitants will suffer.
Deeper aquariums require extra lamps. A good rule of thumb is to
add an extra lamp for each 15 inches of tank over 20 inches high so
that adequate light reaches the plants or reef inhabitants which dwell
on the bottom of the tank.
Glass filters out 95% of all UVB rays unless your tank's glass top
has been specially produced for high quality light penetration.
The amount of time that a tank is illuminated should closely
resemble the native environment of the inhabitants. Since most are
tropical, a 12 hour light cycle (12 light/12 dark) will be fine. There
is rarely any need for your aquarium to be lighted for more than 12
hours, and longer daylight cycles can induce undesirable algae bloom.
| 
