Welcome to the 3rd Pillar of Reef Keeping of this four-part series, where we learn about the latest research about feeding corals and what coral nutrition means for the reef aquarist.
“I thought they only need good lighting?”
In the early days reef keeping there was a theory that captive corals received all their nutrition from the zooxanthellae living inside their tissue. Through photosynthesis, the algae uses waste products from the corals to produce the organic compounds for the corals. Advocates of this idea would say “I only feed my corals light.” – ignoring the fact that the reef is teeming with plankton which corals capture, feed on and digest. There was also a fear that feeding captive corals would overload the aquarium water with organics, stimulate algae growth and make nitrate levels rise. Some reef keepers suggested the corals were just automatically responding to the physical contact with food and don’t really need to feed. But all that changed!
As we’ve seen in the previous parts of this series, we’ve learned a lot more about keeping corals in captivity. We know more about how reef aquariums function and what corals need to thrive. Through a combination of hobbyist trial and error, and scientific research we have a whole new understanding on coral nutrition in the aquarium. Here’s what you need to know about the 3rd pillar of reef keeping.
Corals Must Feed: Supplementing Deficiencies
In nature corals capture and digest algae, zooplankton and suspended particles containing organic matter and bacteria. These foods provide protein, amino acids, carbohydrates, concentrated trace elements and other substances used by the corals. Aquarist observations and controlled scientific studies all show that captive corals capture and consume living and man-made foods. Studies show that symbiotic algae provide their coral host with significant nutrition, but it tends to be low in nitrogen and phosphorus. Nitrogen is needed to form amino acids, proteins and the photosynthetic pigments that give coral their vibrant colors. Dietary phosphorus is required for growth and metabolism. Corals must feed to counteract this nutrient deficiency and balance their energy intake.
“So…. what do I feed my corals?”
Aquarium feeding trials demonstrated that Acropora and Pocillopora fed live Artemia nauplii or unfiltered natural seawater had better growth compared to un-fed corals kept in filtered aquarium water. You probably don’t have access to natural seawater but you can feed your corals with a variety of foods both live and prepared.
A refugium is a great way to culture live foods within the aquarium. It provides a protected environment that acts as a live food farm, releasing a variety of nutritious planktonic organisms into the tank.
You can also feed your corals prepared foods. Liquid foods are a suspension of ingredients formulated to provide the energy building blocks required for coral growth and coloration. These formulations contain carbohydrates, amino acids, vitamins and other compounds that corals normally get from their natural planktonic diet. Liquid foods can be target fed or dosed into the water.
Dry coral foods consist of fine powders made from dried plankton or man-made formulations. The fine plankton-like particles are fortified with vitamins, amino acids, carbs and essential fatty acids. Dry foods are often broadcast into the aquarium’s water where the currents create a plankton bloom for the corals to feed on. You can also target feed a slurry of powder.
Just like many other things in this hobby, what works for one person’s tank, may not work for another’s. There’s no one perfect coral food, even among the available live foods. We recommend experimenting with a variety of food types and see how your corals respond in your reef aquarium.
As discussed in this article, proper feeding is the 3rd Pillar of Reef Keeping. By providing your corals with the nutritional compounds they need, they’re able to resist disease, quickly repair damaged tissue, grow and develop colorful pigmentation. Hope this Chasing Colors, Not Numbers series is shedding some light on how Light, Water Flow and Feeding all work together to give your corals what they need to thrive and produce the vibrant colors you’re looking for as we head into the next pillar. Part 4 of this series will cover the fourth of the Four Pillars: Water Filtration. It sounds simple but it’s something many aquarists don’t fully understand and can prevent their corals from looking their best.