Coral Nutrition and Lighting: Which is better?
As any reefer knows, corals derive their energy from both lighting & nutrition, which are filtered from the water column. Of course, every species of coral needs something slightly different than rest, so how do we decide what our animals need?
Let’s start with lighting. Corals synthesize their own energy in part by harboring zooxanthellae algae, a specialized strain of phytoplankton, within their tissue. As rich-spectrum light penetrates the coral’s tissue, it allows the zooxanthellae algae to grow, thusly feeding the coral. This algae is the very same compound from which coral derives its vibrant colors.
Different wavelengths, or colors, of light have different PAR (Photosynthetically Active Radiation) values (the measure of how intense light is through a medium of water). Just like you learned in high school chemistry class, the spectrum ranges from red, orange, yellow, green, blue, indigo & violet. The lighter colors, red, orange, and yellow, are created by a smoother wavelength of light; whereas the deeper colors of blue, indigo, and violet have a curvier shape to them.
The deeper wavelengths scatter, but have great energy allowing blue light to penetrate deep through the water. Called refraction, this is the reason we perceive the sky and ocean as blue. But ask any diver, and they’ll tell you the light doesn’t appear blue until you reach much deeper depths than where coral are typically found. So what does that mean for coral, which lives 30-60 feet below the surface?
Why do we keep the lighting so heavily skewed toward blue in a reef aquarium? The answer isn’t as profound as you may think: It looks great!
The richly bright fluorescent colors most corals sport are devolved by specialized chromophores intended to absorb or reflect the most optimal light spectrums that are available at such depths. The darker, more prominent coral colors, such as brown and purple, can absorb more of the readily available red, orange & yellow wavelengths capable of eking down to those depths; where as the metallic red, pink & orange pigments reflect the bombarding blue light. The decreased red & yellow spectrums, though intensify the brighter pigmentation of the coral, can unfortunately decrease the coral’s ability to rely on production of it’s zooxanthellae algae.
Unfortunately, as aquarium lighting leans more towards the deep blue wavelengths, there isn’t always enough full spectrum light to keep the coral healthy with lighting alone.
Corals, like every other animal, must eat. They need a wide range of food easily available to them. Luckily, every species of coral feeds on single celled, energy-rich algae. Additionally, both fresh phytoplankton and the coral’s own zooxanthellae algae are critical for its survival. The phytoplankton is thankfully all-purpose; they feed every single species of coral in the ocean. On top of that, several species, such as Gorgonians, Carnation Corals, other non-photosynthetic corals, and Clams only feed on phytoplankton. Without phytoplankton, these species cannot survive.
Still other corals like to feast on zooplankton. Zooplankton are microscopic to macroscopic animals like rotifers, daphnia, copepods & amphipods. Depending on the size of the coral’s polyps, different sizes of zooplankton must be made available to feed the inhabitants of one’s tank. Smaller polyps, such as those on Acropora and Montipora, will obviously do well on smaller zooplankton, like rotifers. Consequently, large polyped-coral, such as brain corals, do well feeding on meaty zooplankton, such as copepods.
There are several options when it comes to feeding your coral. Although there does happen to be several dried or inert (dead) liquid diets readily available as feed, any reefer will be quick to point out that those don’t even compare to live food.
As with any filter feeding invert, corals eat slowly over a period of time. Dead foods quickly settle to the sand bed, or get sucked into the filter not long after feeding. The result? Even more buildup of waste in the aquarium. Live foods, however, actually aid in removal of harmful elements from the aquarium up until the point they’re eaten. With live feed, you’ll even create a sustainable food source; phytoplankton and zooplankton reproduce like crazy.
With proper lighting, placement & high-quality live food, your coral can be vibrant, thriving, and happy, just as nature intended.