Light
The supply of sufficient photons of wavelengths between
400 and 700 nm is important for maintaining coral health
and achieving maximum growth....
Not all photons equally promote coral growth. Kinzie
et al. (1984) noted the association of the primary photo-
synthetic pigment chlorophyll a, with blue light (430–
495 nm) absorption. When examining the growth perfor-
mance of Acropora solitaryensis Veron & Wallace, 1984
grown ex situ under four metal halide treatments (150 W
bulbs with Kelvin ratings of 20 000, 14 000, 10 000 and
5000 K), Schlacher et al. (2007) found the highest growth
rate under 20 000 and 14 000 K bulbs which contained
more blue light than the other treatments. Not only does
blue light appear to enhance the growth and survivability
of stony corals, but red light (~630–690 nm used) may
repress the photophysiology of scleractinian corals as
observed in S. pistillata (see Wijgerde et al. 2014). It is
important to note that emission spectra and irradiance are
variable between different brands of bulbs advertised with
the same colour temperature.
Practical sources of light provision include metal halide,
T5 high output fluorescent, LED (light emitting diode)
and light emitting plasma (LEP). LEP and LED light
sources are cost–effective because they use less power to
achieve the same irradiance as other light sources (T5 and
metal halide) and thus can support the sustainability and
viability of ex situ coral propagation (Rocha et al. 2013a)
This may be
attributed to the broad emission bandwidth of LEP mod-
ules compared with the narrow bandwidths emitted by
the three colours of LEDs used (white, blue and royal
blue). However, Rocha et al. (2013a) found slightly higher
growth with blue LED lighting compared with LEP light-
ing for A. formosa and S. pistillata fragments. They assert
the importance of more research in determining the suit-
ability of LEP and LED lighting in the culture of more
species of scleractinian corals. The utilisation of a larger
variety of LEDs within LED modules could potentially
increase performance. Additionally, individual LEDs can
be easily retrofitted with optics which focus the light into
cones of emittance (e.g. 60°optics). This is common in
the aquarium industry and can increase the efficiency of
LED lighting applications by not ‘spilling’ photons away
from where corals are located
