LED optics can be either lenses or reflectors. Lenses
tend to be more efficient than reflectors at shaping the
light beam. Collimators are lenses that can be used to
change the beam angle and the divergence and shape of
the beam. They are typically designed for specific LEDs
and must be used in conjunction with those LEDs. A
typical design is a collimator lens that spreads the light
on the surface in a specific angle. Collimator lenses are
available in varying angles, and they can be made of glass
or optical plastic (such as acrylic or polycarbonate). The
choice has an impact on the manufacturing (and subse-
quent retail) cost and quality. Tertiary optics are used to
further vary the distribution of light and may protect the
elements of the LED system.
Figure 8: The graphs show that the
currently available LEDs are perfectly
capable of providing the amount of
light required. The data are based on
the light distribution of an ACAN LED
lamp (see photo, right), also available
in the trade under the product name
KR- 92, with housing dimensions of
around 24 x 8 x 1½ inches ( 60 x 20 x
3. 5 cm). It contains 91 LEDs (around
two-thirds white, one-third blue)
and has a power consumption of
100 watts. These graphs show that
at a distance of 30 inches ( 76 cm)
the lamp will illuminate an area
measuring 24 x 18 inches ( 60 x 45
cm) with more than 100 µmol/m2/s. If
the distance is reduced to 24 inches
( 60 cm), the intensity of the light
increases while the area illuminated
becomes smaller. Because the LEDs
do not radiate any heat (infrared), the
light can be mounted considerably
closer to the water’s surface than
other types of lighting. Two such
lamps would be adequate for a
reef aquarium measuring 48 x 18
x 24 inches ( 120 x 45 x 60 cm). The
aquarium pictured at the beginning
of this article contains numerous
different coral species illuminated
with these lamps.
Low;light
Medium;light
High;light
Very;high;light
Corals;and;their;light;requirements
Mushrooms, zooanthids, soft corals
LPS, some SPS
Acropora, Montipora, SPS, clams
Very few SPS
μmol•m2•sec
50–100
100–200
200–500
600– 1,000
