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. Of course, this formula has certain limitations and must be
adjusted to allow for very small aquariums or those that are deep.
Also, if using a high output fixture (vho, metal halide), 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 10 watts per gallon 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 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 is 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
and available in a wide range of wattages and color
temperatures. 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 recently
been eclipsed by the popularity of a newer technology, the T-5 high
output fixture. 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.
Metal
Halide
For a large
marine planted aquarium there probably is no 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. 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.
LED High
powered LED lighting is a fairly new technology for the aquarium
industry. They are very efficient fixtures, using about 70% less
energy than a typical metal halide fixture. Because they are not
actually bulbs, they require a lot less power to run as well as
much less heat. The fixtures can be mounted closer to the surface
of the water so they also are better at penetrating deep tanks.
The are among the most expensive light fixture available for the
aquarium, so for most hobbyists they would not be the first choice
to illuminate refugiums and planted aquariums.
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