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Spectrum Spectrum
ratings are listed by the Kelvin temperature scale. The lower end of the Kelvin temperature range bulbs
are
most suitable for growing marine plants and are available in 5000K
- 6500K. If your aquarium
will include soft corals, most marine plants will also grow under
10,000K lighting. This is normally a more pleasing spectrum to the
eye, as the
lower temperature bulbs can appear green or yellow. Unlike
terrestrial plants, macro algae react differently to varied
spectrums of light and the changes in color among different
species can be quite dramatic. There are a few varieties of red
macro algae, for instance, that can be found in shades of red,
yellow and brown within the same species. The distinct coloration
is caused by the pigments associated which each species and the
spectrum of available light it receives. Overall most macro algae
and sea grass will do well under full spectrum lighting or 6500K.
The exception is with some varieties of red macro algae, which
prefer a much bluer spectrum and can benefit
from actinic lighting in the 8000K range. Mixing bulb
color temperatures is preferred and is the most appealing while
still allowing for optimum growth. Intensity The
same rules that apply to freshwater planted systems and some soft
coral dominated aquariums translate to the marine planted aquarium
and or refugium. As a general rule, most marine plants and algae
need roughly 3-4 watts per gallon of full spectrum lighting to
grow. This is an older formula that has certain limitations and must be
adjusted to allow for very small aquariums or those that are very deep.
Also, if using a high output fixture such as metal halide
lighting, less watts per gallon
are generally needed. A few deep water species can do well in low
light conditions, but will grow much slower in this environment.
Sea grass however, need large amounts of intense full spectrum
light, as much as you can give them to thrive. Duration Most
tropical regions receive approximately 12 to 14 hours of daylight,
with 8-10 hours of intense light, followed by 10 hours of darkness
each day. While certain macro algae can receive constant
illumination, such as many species of Caulerpa, the benefits are not well
documented and growth rates are often affected. Most macro algae
and all terrestrial plants need a time to rest as they still
continue to respire after photosynthesis has ended. Generally a
duration of 12-14 hours is sufficient for growing macro algae and
sea grasses. Unlike terrestrial plants, algae need a steady duration
of light in order to undergo photosynthesis. A simple timer is all
that is needed to maintain a constant, stable environment. If
growing marine plants in a refugium, it is generally acceptable to
have the lighting on a reverse cycle so that when the main tanks
lights are off the refugium lights turn on. This is reported to
help with the stabilization of ph levels and the overall safety of
its inhabitants as marine plants absorb oxygen during the night,
effecting the ph. Suitable
Lighting  The most common types of
fixtures available to light a refugium or marine planted aquarium
include normal output fluorescent, high output fluorescent, power
compact fluorescent, T5 high output fluorescent and metal halide
light fixtures. The
brightest are the metal halide fixtures and the least bright are
the standard output florescent fixtures. While these are all
suitable for growing most varieties of macro algae some will
produce more growth and improved coloration with more intense
fixtures. LED light fixtures are a new technology that a few
reef aquarium hobbyists have begun using with good success. While
this type of fixture is still in its infancy, it may in time
become an economical option for providing photosynthetic organisms
the light they need with drastically reduced energy consumption
and heat exchange. In addition to selecting a proper fixture, the
most efficient bulbs have a high CRI (color rendition index) or
PAR (photosynthetic active radiation) value and offer the hobbyist
the most beneficial light available to marine plants.
Compact
Fluorescent This
fixture used to be the most
economical lighting option for growing marine macro algae and sea
grasses in the aquarium. They have roughly 3x the output of
standard fluorescent bulbs and are efficient at providing intense
light in small spaces which make them ideal candidates for use
over a refugium. The bulbs and fixtures are relatively inexpensive
but have recently fallen out of favor due to the high cost of
replacing the bulbs. They're still available to the hobbyist and
come in many different spectrums. High
Output Fluorescent These include
very high output (VHO) and high output (T-5 HO). VHO lighting is
an excellent fixture for growing marine plants, but has been
replaced by the popularity of the T-5 high
output fixture and of course the LED. Similar in intensity to the power compacts, the
advantage of the T-5 is that the amount of light is spread more evenly
over the aquarium. They are also more economical and take up far
less space than traditional T-12 and T-8 bulbs. The bulbs are
available in a wide range of spectrums including those in the
5000K - 7000K range ideal for marine plants and macro algae. Some
hobbyists continue to use them today, especially in commercial
coral farming.
Metal
Halide
If
you can afford the high cost of running them, for a large
marine planted aquarium there probably isn't a better lighting
source than the use of a metal halide fixture. Metal halide offers
the aquarist the closest spectrum to natural sunlight available
and adds a shimmering, rippling effect that is not duplicated by
any other type of bulb including LED's. Depending on the size of the tank, metal
halides are available in single ended and double ended bulb
styles. Double ended or HQI fixtures are the most efficient and
generate considerably less heat than the older probe start
ballasts. As of today, most hobbyists have stopped using this type
of fixture due to the very high energy costs associated with
operating them. I really do miss using them in our facility as we
were able to grow some beautiful healthy specimens but they simply
became to costly to operate.
LED High
powered LED lighting has come a long way since their introduction
some two decades ago. They're arguably the most energy efficient
fixtures available to the hobbyist, using about 70% less
energy than a typical metal halide fixture. Because they're not
actually bulbs, they require a lot less power to run and produce
less heat. The fixtures can be mounted closer to the surface
of the water so they can penetrate deep tanks. The diodes do last
quite a long time but start to degrade after a few years and begin
to lose the spectrum and par. They will never provide the same
useful wave length for photosynthesis that metal halides can
provide but most marine plants adapt very well to the full
spectrum wave lengths. We use the COB flood style led fixtures
with reflectors in our facility and they do a pretty good job at
keeping specimens alive and growing.
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