*main image credit to Evan Suh
Gorgonians are a mysterious and often misunderstood type of soft corals. They come in myriad shapes and colors, but the most familiar of them to the aquarist might be the Caribbean photosynthetic varieties, such as Eunicea mammosa — the Swollen Knob Candelabrum, Pterogorgia sp. — the so-called sea whips/ribbons, or the Rusty Gorgonian — Muricea elgongata, to name just a few.
The types of Gorgonians found in the hobby can broadly be divided into two categories: photosynthetic and non-photosynthetic (NPS). NPS gorgonians do not have Dinoflagellate symbionts populating their soft tissues, converting light energy to glucose, bestowing energy to the coral animal. Rather, all their energy is derived from food in the surrounding water column, which presents the aquarist with problems. Most photosynthetic Gorgonians may be plopped into a tank with little care taken for their needs; if there is moderate flow and clean water, they will do well. NPS Gorgonians, on the other hand, require an extraordinarily specified diet; thus, the natural question becomes, what do they eat?
Swiftia sp. photo credit to Levi Peterson
In order to understand what NPS corals eat, it is imperative to understand the environments they are endemic to in the wild, for they thrive there. Take Muricella, for example – a beautiful burgundy-pink net of anastomosed branchlets in the family Acanthogorgiidae, shaped like a baseball mitt, which plays host to the famed pygmy seahorse. These corals, according to Matt Wandell, Project Manager at the Monterey Bay Aquarium, come from the mouths of tidal coves where inflow and outflow during tidal shifts are blazingly fast. No doubt the net shape of the coral serves its purpose, catching every morsel of zooplankton as it rushes by twice a day.
What can we learn from this example? First, it must be very important to provide Muricella with exorbitant amounts of zooplankton. Second, it likes very high flow. These precepts are a decent starting point, but can we dig further? Might the species of zooplankton that compose Muricella’s bulk diet be easily obtainable knowledge? Will such knowledge help keep the coral alive?
These are not easy questions. If you wanted to answer them, you might scan the Google Scholar search engine for scholarly articles on Muricella, create a list of the locations studied in several articles, and then try to find zooplanktonic surveys of the same locations. Many zooplankters perform Diel vertical migrations – a 24-hour cycle wherein organisms migrate from depth to the surface, then back down again. So, there are only specific species of zooplankton present in the water column at the times when tidal inflow and outflow are occurring, according to the Diel cycle. This makes answering our question even more difficult. Answering what seemed like a simple question now has become a time-consuming, laborious process, and even if you figured out what the most abundant copepod in Muricella-populated waters is during inflow and outflow times, how are you going to culture it? Where can you buy such copepods? Surely, they are not commonly sold in the hobby. This is a dead end. So, what is the solution? – Possibly, Artemia nauplii (baby brine shrimp).
A red Muricella plectana with a pair of H. bargibanti original source = https://reefbuilders.com/2018/05/23/muricella-pygmy-kingdom/
Decapsulated Artemia nauplii have been shown as a suitable food source for these corals. They must be decapsulated, as the egg cysts can clog the digestive tract of gorgonians. They must be fed in very large quantities at least three times per week. This means NPS gorgonians are not for the faint of heart, as the aquarist must hatch baby brine on a weekly basis. Once hatched, the aquarist should filter the Artemia nauplii through a 53-micron sieve, then wash them into a small vessel with tank water. At this point, tank flow may be turned off, and the Artemia nauplii may be gently pipetted into as many polyps as the aquarist has patience for (the more, the better). Tip: feed your fish first so they don’t start nabbing at the polyps for a snack.
Such a methodology may be a plausible solution. One might even improve the solution by gut-loading the Artemia: letting them swim around in phytoplankton for several hours before feeding them to Gorgonia, thus loading their bellies with nutritious, algae-born fats.
The issue is that solving a problem such as this is unique to each type of “expert-only” NPS coral, not just gorgonians. We could have performed the same process for Dendronephthya, considering flow, pelagic bacteria, and phytoplankton species as we did for Muricella, having considered flow and zooplankton species. The point is that the aquarist must do their research. They must read scientific articles. They must listen to the word of divers, if not dive themselves. They must consult with other aquarists. They must devote themselves to reef-keeping, absorbing every bit of relevant information like a sponge. It is a never-ending process, and even then, the aquarist might fail; these corals are not for everyone. Thus, my hope with this article is twofold: to dissuade the uneager from ever keeping NPS corals—if you don’t take meticulous care of these animals, they will die—as well as to inspire those who are eager for a challenge to make an attempt at their husbandry.
Image Credit to Florian Gaudig
The world is losing corals at an alarming rate. It is estimated that the dominant reef-building coral of the Caribbean, Acropora palmata, the famed Elkhorn coral, has been reduced by 98% since the early 1980s. Corals are important to the world, and humanity should help prevent their extinction to conserve their ecological and global benefits for the Earth’s system. Corals sequester the greenhouse gas carbon dioxide from the atmosphere, helping to reduce its increasing concentration, which contributes to anthropogenic global warming. They have been termed “ecosystem engineers,” as they provide habitat not only for the cute pygmy seahorse but for over half the world’s harvestable global fish stock – that’s right, destroy the corals, and now over 1.5 billion people in coastal nations will struggle to find food. Corals provide novel health benefits. Big-name pharmaceutical and cosmetic companies have staff scientists studying these corals for their unique biochemistry with hopes of deriving the most effective facial cream or cancer treatment. Coral reefs act as a natural breakwater. Their calcium carbonate (limestone) skeletons push back against the strong waves of hurricanes, preventing billions of dollars of storm surge damage. Lastly, let us strive to preserve these corals for their extreme beauty. We should want to leave the world a better place so our children and grandchildren can be in awe of how beautiful a place Earth really is, and maybe the corals will inspire them to improve it as well.
I thus urge aquarists to attempt to keep these difficult, non-photosynthetic corals responsibly. You will further drive the market towards revolving around them if you do so, which is not a bad thing. Market-based solutions can solve real-world issues. The first sexual reproduction of corals in a lab was made possible only with the knowledge and technology of the hobbyist trade. Massive projects are underway to sexually reproduce stronger, more heat-resistant, and ocean acidification-resistant strains of coral to be out-planted in the wild. The hope is that by engineering a stronger coral, humanity may preserve its reefs and their multitudinous, varied benefits for coming generations. The companies that produce the hobby’s equipment are what allowed this great scientific advancement to occur, yet they would not exist without you, the aquarist.
Acanthogorgia sp. (Image by Damien Brouste) https://www.inaturalist.org/observations/199351936
Lastly, the difficult struggle of the hobby, the uneasiness of not knowing if your idea will pan out, the strain of tirelessly working and striving to conceive of the best plan of attack, and the connections fostered via this process are what make the reef-keeping hobby go round. It is our passion that inspires and pushes the hobby forward into the future. It is uncertain what the benefits of more people keeping NPS Gorgonians will be, but perhaps, somewhere along the way, a brilliant mind will come along that changes the world. Let us all strive to help them achieve this goal. Let us change the world together.
About The Author
Julien Napoli worked as an aquarist and aquaculturist for multiple years at Absolutely Fish in Clifton, New Jersey, a Marine Aquarium Council (MAC)-certified and nationally recognized local fish store and aquaculture facility. He is a United States Navy veteran and will soon be earning his bachelor’s degree in Earth Science from Columbia University, where his research has focused on the implications of stable coral-skeletal carbon isotopes in paleoclimatology.
