What Kind of Light Do I Need for a Refugium?

Nowadays, almost all refugia have macroalgae and other types
of plants in them. This means that they require a light source of their own.
Luckily, there are now aquarium lighting systems that are specially designed to
provide the very high intensity needed for this as well as a plant-specific
spectrum. Moreover, the very best of these specialized fixtures (for example,
the ChaetoMax
Refugium Light
) are made to fit nicely into the often clamped overhead of a
refugium space.

Being as your planted refugium will probably be the single
most important component of your aquarium’s life support system, and lighting
quality will affect its performance more than anything else, we should
elaborate on this a bit.

No refugium macro can do its job, much survive, unless it
receives sufficient photons to carry out photosynthesis. The compensation
intensity is the minimal amount of light a plant must receive for its gross
rate of photosynthesis to equal its gross rate of respiration. In other words,
it needs just enough light energy to make just enough sugar to at least
maintain its basal metabolism. Growth occurs only after the compensation
intensity is exceeded. The uppermost growth limit is reached at the saturation
point; this is the intensity at which its photosynthetic machinery is working
at maximum capacity.

Let’s just put it plainly here: Natural sunlight is
incredibly bright. You’re never going to reach anything near the saturation
point using an aquarium light. The bigger worry should always be providing enough light, not just for survival but for good growth. Only continuous growth will
result in continuous nitrate and phosphate removal! To achieve
this--maximally--you’ll want to be sure that your seaweed bed is illuminated
not only at the surface but all the way through to the bottom. This usually
requires at least as much intensity as one might use to grow SPS corals!

In addition to high intensity, try to get a light that is
designed specifically for plants. These types use only red and blue lights
(plants generally don’t use other spectra) as to maximize the efficiency of the
fixture. Thus, while they look a bit unnatural to the eye, these lights promote
the highest growth rates for your plants.

Finally, one big advantage of using a light fixture
customized for refugia is that their housing is typically very compact. They
might also have extremely adaptable mounting/positioning options. This means
that you’ll be able to fit the light into a small area (e.g. within cabinetry)
and spotlight the grow space exactly as you desire!