A Quick Guide to Keeping Photosynthetic Gorgonians in Home Aquaria
Hello fellow reefers! My name is Billy and I am a big fan of the beautiful, tree-like soft corals known as gorgonians. Despite their reputation as delicate animals that are difficult to keep in captivity, most photosynthetic gorgonians are extremely hardy, and some even make excellent starter corals for those just getting into the hobby. With this in mind I decided to create this quick and dirty guide to encourage more home aquarists to experiment with keeping these wonderful animals, as I consider them to be some of the most captivating and attractive corals in the sea.
Eunicea flexuosa, a beautiful photosynthetic gorgonian.
1. What is a Gorgonian?
Gorgonians are colonial soft corals that belong to the order Alcyonacea. They are closely related to other softies such as leather corals (Sarcophyton, Sinularia, Capnella, etc.). They generally exhibit upright, branching growth patterns that make them look a lot like underwater bushes or trees, and attach themselves to hard surfaces with a matlike holdfast. Though some gorgonians incorporate calcified spicules into their tissues, most do not lay down a hard skeleton of calcium carbonate like reef-building corals do. Instead, their skeleton is made from a strong, flexible protein called gorgonin, around which the fleshy structure of the animal grows. Gorgonin is similar to the material found in human tendons, but has about twice as much tensile strength. This supple skeleton allows gorgonians to bend and sway in the current, evenly exposing the polyps on both sides of the colony to light and nutrients. Gorgonians and other Alcyonaceans are sometimes referred to as octocorals because their polyps have eight-fold symmetry (e.g. the number of tentacles on each polyp is always a multiple of eight). All gorgonians catch and eat plankton, and some also have symbiotic dinoflagellates called zooxanthellae that live inside of their tissues and make energy for them using sunlight. This article will focus on these photosynthetic species, as they are generally hardier and easier to keep in captivity than their azooxanthellate relatives.
Photosynthetic gorgonians inhabit shallow tropical seas around the world, but a large majority of them come from the tropical Western Atlantic - namely the waters around Florida, the Bahamas, the Gulf of Mexico, and the Caribbean Sea. In the Indo-Pacific the same shallow, brightly-lit, wave-washed environments that Atlantic gorgonians call home are instead inhabited by various leather corals, which are not found in the Caribbean at all. The opposite is also true, with gorgonians being quite uncommon (though not entirely absent) in the Indo-Pacific regions where leather corals rule. The vast majority of the various species of photosynthetic gorognians available to hobbyists come from the waters around Florida and the Caribbean Sea.
2. Care Requirements
Most photosynthetic gorgonians are hardy and fairly easy to keep, but they do have a few specific care requirements to keep in mind. First and foremost is flow. Almost all gorgonians like fairly robust water movement, but too much flow can interfere with their feeding. Flow should be strong enough to stir the colony's branches but not so strong that the animal is blowing over or knocking into its neighbors. If you notice that your gorgonian's polyps are struggling to open or are periodically shutting and then opening again as the colony is buffeted by the current, then you may want to dial down your flow a bit. Indirect, semi-randomized flow is generally best; most of the time it is better to bounce flow off the glass or rockwork rather than pointing a powerhead directly at your gorgonians.
Also, most gorgonians prefer to be oriented perpendicular to the current, with the flow passing over and through the mass of their branches. In nature these animals often inhabit shallow hardbottom areas that are swept by strong, uni-directional laminar currents which reverse periodically with the changing of the tides. A setup involving two wavemakers at opposite ends of a long tank that provide alternating flow throughout the day would be ideal for most gorgonians, but in smaller systems where this is not an option a single powerhead is generally more than sufficient as long as it is positioned properly. Many of the more fan-shaped species also enjoy wavelike flow patterns that cause their branches to flap back and forth from side to side. This motion ensures that the polyps on both sides of the animal are alternately shaded and exposed to light, maximizing the colony's potential for photosynthesis.
Photosynthetic gorgonians of course require sufficient light to grow, and most of them can handle quite a bit of it. Many genera commonly found in the aquarium trade (e.g. Pterogorgia, Eunicea, Muriceopsis) come from very shallow water and are regularly exposed to intense sunlight. Some can tolerate a bit less light though, and pretty much all gorgonians are considered less picky about light than SPS or even LPS corals. Generally speaking any light strong enough to keep LPS corals like Blastomussa etc. is probably good enough for gorgonians as well. I keep mine under a 15 watt Kessil A80 LED, and even this fairly weak light has given me good results so far.
Like most zooxanthellate corals, gorgonians will take some time to adjust to your aquarium's lighting regimen after being added to your tank. Under bright lights newly introduced colonies will sometimes expand the polyps near their base first, with extension working up the colony's stalk as it becomes accustomed to the light. Some species are a bit more picky than others of course, so monitor your new arrivals carefully to ensure that they are not getting blasted with too much light. Gorgonians that are receiving excessive light will often not expand fully despite adequate flow, or will become overgrown with algae. Positioning your gorgonians in such a way that light and flow are "just right" can be a bit challenging, but once a balance is struck they tend to do well for a long time provided conditions do not change.
Despite what much of the traditional wisdom involving these animals suggests, all gorgonians, photosynthetic or otherwise, are active planktivores and should be fed with some sort of dissolved micro-food on a regular basis. I feed mine Reef Roids and pulverized PE pellets, but any similar coral food will likely work just as well. Generally speaking the larger a gorgonian's polyps, the more it benefits from feeding; in fact some very large-polyped varieties (e.g. Eunicea) will even eat normal fish foods like whole pellets, flakes, or mysis shrimp. One or two feedings a week should be fine for most photosynthetic species, though more frequent feeding will stimulate rapid growth.
During feeding, I recommend turning off your aquarium's circulation pumps and target-feeding each gorgonian individually using a pipette or turkey baster. All polyps in the colony share resources with each other, so don't worry if you don't get food to every single one. Leave your pumps off for ten minutes or so after feeding to allow the animals to eat, then turn on your powerhead or wavemaker for another ten minutes to circulate floating food particles throughout your display. It is best to keep your return pump off for the entire duration of the feeding to prevent food from being carried away into your filtration media. Just don't forget to turn the pump on again when the feeding is done!
The large polyps of this Eunicea sp. are well adapted for catching plankton.
As with any animal a varied diet is best, so combining microalgae/phytoplankton-based foods with zooplankton-based foods is always a good idea. The absolute best option would be to feed your gorgonians a combination of home-cultured live microalgae plus small planktonic animals like rotifers, copepods, or Artemia. We have a number of good growing guides here on N-R for culturing live foods in case you're interested in taking this extra step. 😉 @seabass's guide to culturing phytoplankton is a great place to start!
IV. Water Quality
Photosynthetic gorgonians are hardy by coral standards, but they still require a well-established aquarium with stable parameters. I do not recommend adding gorgonians to tank that is still cycling / might not be cycled all the way yet / has just finished cycling. Let things settle down and get into a normal, predictable rhythm before adding gorgonians to your system. "Dirty" water with lots of organic nutrients is often not that big of a deal for these animals (in fact having "zero" nitrates and phosphates is almost certainly bad for them), but it's important that parameters remain stable. The calcium, alkalinity, and nutrient levels in the average mixed reef aquarium are more than adequate for most photosynthetic gorgonians, so just aim for whatever levels work for the rest of your livestock and you should be okay.
One element that bears special attention is iodine. The protein that gorgonians use to build their skeleton contains a considerable amount of iodine, and maintaining adequate levels of it (usually by supplementing it in the form of iodide) likely has a positive impact on their growth. Many smaller reefs have their iodine levels depleted rapidly, especially if they contain a variety of iodine-hungry soft corals and mushrooms, so supplemental dosing may be necessary to keep up with consumption. Just remember that excess iodine in the water is toxic to many animals, and too much can even kill the bacteria that make up your biological filter. It is therefore a good idea to keep careful track of iodine consumption and only dose as much as is necessary to keep your levels around 0.06 ppm (which is the concentration of natural seawater). Blind-dosing of iodine can be dangerous and is not recommended.
That being said, most photosynthetic gorgonians can certainly be kept in low-maintenance setups that dose nothing at all, so long as a simple regimen of regular water changes is observed. Dosing iodine is simply an option to accelerate their growth.
V. A Note on Sloughing
Many species of gorgonians periodically shed a waxy film off their surface to prevent algae and other sessile organisms from colonizing their bodies. At the start of the shedding process a colony may close its polyps for a number of days or sometimes even weeks before sloughing off its outer layers. Don't be alarmed if this occurs in your aquarium from time to time, as it is a natural process that is essential for the proper health of your gorgs. If you notice ribbons of waxy gunk hanging off your gorgonians, try gently squirting them with a turkey baster to speed the process along.
3. Reproduction and Propagation
Gorgonians in the wild can reproduce sexually by spawning, but the most common method of reproduction both in the ocean and in aquaria is asexual reproduction by fragmentation. In nature gorgonians are periodically pounded by storms and strong waves that scatter their branches about, and some even encourage this process by intentionally weakening their own branches or dropping little bits off of themselves. Each piece that lands in a favorable location has the potential to grow into a clone of its mother colony.
Many gorgonians sold in the aquarium trade are specimens that were propagated by fragmentation. For most photosynthetic gorgonians this process is quite easy: simply snip off a branch from the main colony with scissors, glue it down to a rock or reef plug with gel superglue or underwater epoxy, and place it in a suitable location in your aquarium. As long as conditions are right the fragment should establish a holdfast and begin growing fairly rapidly. The main colony should also regenerate quickly; in fact some species from the genus Antillogorgia have even demonstrated increased growth after injury compared to intact colonies.
4. Aquascaping With Gorgonians
Positioning gorgonians in your aquarium can be somewhat challenging, but when successfully incorporated into an aquascape they are breathtakingly beautiful. Photosynthetic gorgonians can be kept in practically any size aquarium, but tanks of at least 10 gallons are recommended as most gorgonians need to reach a reasonable size in order to demonstrate the full effect of their lovely branching growth patterns.
Combining multiple species of photosynthetic gorgonians can make for a lovely display.
There are a number of ways to incorporate gorgonians into your aquascape, and how you go about doing so will largely depend on your other livestock and the layout of your rockwork. With their beautiful swaying motions and soft, fuzzy polyps, gorgonians are an excellent way to provide movement and fill vertical space in your tank. They must however be given adequate room to sway in the current, and care must be taken to ensure that your gorgonians are not touching or rubbing against anything else in the tank, especially not other corals. Gorgonians of different species will usually sting each other if they touch, and even members of the same species will retract their polyps in places where they rub together. The sting of most gorgonians is quite weak, so they tend to lose coral wars with pretty much everything. Keep this in mind when positioning them in your tank.
You'll also want to make sure that your gorgonians are oriented perpendicular to the current, and that they have adequate access to light. Many gorgonians grow quite quickly, so be mindful of their potential to eventually shade out other corals below them. Most gorgonians can be trimmed back without ill effects if excessive shading becomes a problem, but it's best to avoid this issue altogether by positioning them carefully from the get-go. All gorgonians must be attached to a hard substrate like a rock or a reef plug, so don't attempt to bury their bases in the sand. In addition each individual species of gorgonian has slightly different positioning needs based on the habitat in which it is commonly found in nature. Many Antillogorgia spp. for example like to grow horizontally out of vertical rock walls with their plumes reaching sideways into the current. Doing some research on the specific species you'd like to keep and orienting them accordingly can help increase their chances of success in your aquarium.
5. Hardy Starter Species
If you're interested in keeping photosynthetic gorgonians in your tank, several good entry-level options are detailed below. I have kept most of these species myself and have had good results with them so far.
Antillogorgia spp. (formerly Pseudopterogorgia)
Common names: feather gorgonian, sea plume, purple frilly gorgonian
These beautiful featherlike gorgonians grow very rapidly under good conditions. They are usually some shade of purple, but yellow varieties are also available. Polyps are generally cream-colored or brown. Many species of Antillogorgia like to be oriented diagonally or horizontally, with the main axis sticking out sideways into the current. They do best under fairly bright light and can tolerate strong water movement. Algal growth can sometimes be a concern with this species, so keep an eye on them and make sure they don't become overgrown with cyanobacteria or diatoms. Use a soft brush or turkey baster to blow diatoms off their branches. Some species (e.g. A. bipinnata) can grow to a considerable size.
Common names: purple plume, purple bush
M. flavida is the first gorgonian I kept, and is one that continues to do well in my tank to this day. It has a beautiful purple color with very fuzzy brown polyps. This species can tolerate rather less water motion than others (though it does just fine with plenty of flow as well), so it may be a good choice for those with smaller aquariums or setups that require less flow.
M. flavida seems to have an interesting habit of dropping the tips of its branches from time to time. I believe this is an example of propagation by intentional self-fragmentation. This freaked me out at first because I could not understand why pieces were falling off my otherwise-healthy gorgonian, but after months of observing this specimen I have decided that it's simply a normal behavior and is probably nothing to worry about.
Common names: sea whip, ribbon gorgonian, cactus gorgonian
This cactus-shaped, straplike purple gorgonian is one of the hardiest species around. It sheds an especially thick waxy film from time to time, which helps it resist algal growth in the shallow, brightly-lit waters it calls home. I have read reports of this species gradually declining over time in aquaria because it requires very strong light and needs robust water movement to assist with its heavy shedding regimen, but so far I have not had any problems with it myself. It is also notable for being a very sturdy shipper. This species seems to benefit greatly from supplemental feeding with fine planktonic foods, so don't forget to feed it once or twice a week.
Another species from this genus, P. citrina, is also occasionally available in the hobby. It is yellow rather than purple, has thinner blades, and generally exhibits a more bushy, less elongated growth pattern. It is slightly more delicate than P. anceps but its care requirements are generally similar.
Common names: spiny bush gorgonian, rusty gorgonian
M. elongata is an attractive orange or rust-colored gorgonian with projecting calyces (the small cuplike projections that house its polyps) that give it a spiny appearance. This species seems to like fairly strong indirect flow and moderate to bright light. It does not seem to shed very often at all (in fact I can't recall ever seeing it do so), but nonetheless appears to have no problems keeping itself free of algal growth. With its polyps extended it looks very attractive indeed. Muricea have a bit of a reputation for being poor shippers, but if they survive the first week or so in your system they are likely to do well for a long time.
Another species in this genus, Muricea laxa, is also available in the aquarium trade. It has a beautiful silvery-white coloration with tan or brown polyps. M. laxa comes from deeper water and is much more rigid than the fairly flexible M. elongata. It is known to be a more robust shipper than other Muricea.
Common names: sea rod, candelabra gorgonian
The genus Eunicea contains a number of very large gorgonians that can reach heights of more than a meter out in the wild. Most species have thick, cylindrical branches with large fuzzy polyps. They generally start out as single rods that begin to branch (usually in a single-planed candelabra pattern) as they get older. These gorgonians can handle a lot of water movement, but care must be taken to ensure that their long branches do not rub against their surroundings as they blow around in your tank. Growth can be quite quick once established, and colonies that get too large are easily pruned by simply cutting their branches with a pair of scissors. The resulting fragments can be glued down to a piece of rock or a reef plug to propagate the colony. Eunicea seem to ship fairly well, with the exception of one species: E. flexuosa (formerly Plexaura flexuosa). E. flexuosa is a gorgeous gorgonian, but has a tendency to get quite brutalized in shipping. Mine lost multiple branches and took a month to settle down after being added to my tank, which is an extremely long time by photosynthetic gorgonian standards.
Common names: Grube's gorgonian
A beautiful Grube's gorgonian from N-R member @lizzyann's mixed reef aquarium. Photo from her aquarium journal.
Grube's gorgonian is one of the few photosynthetic species from the Indo-Pacific that is commonly available in the hobby. It has a bushy growth pattern and seems to grow very rapidly under favorable conditions. I have not kept this species myself, but several gorgeous reef tanks here on Nano-Reef feature this species so I think that it bears mentioning here. It seems to be quite hardy and has fairly standard care requirements for a photosynthetic gorg. Grube's gorgonian has been popular in Europe for some time, but has only reached American markets relatively recently.
6. TOTM Gorgonian Gallery
Looking for some great examples of beautiful reef tanks that highlight photosynthetic gorgonians? I've included a few of my favorites from Nano-Reef's Tank of the Month (TOTM) archive below! Many of these systems have given me a lot of inspiration, so I hope they will do the same for you.
(Sorry for not tagging everyone; some folks from older TOTMs have since changed their name and no longer show up on a tag search 😅)
trueisb2's 20 gallon nano reef (September 2012)
Ziareefer's 50 gallon seahorse and gorgonian tank (February 2014)
trueisb2's 3.5 gallon pico (March 2014)
References and related reading:
Sprung, Julian and Delbeek, J. Charles. The Reef Aquarium, Volume II. Ricordea Publishing, 1997.
Sprung, Julian. "Aquarium Invertebrates: Caribbean Gorgonians: Beauty in Motion." Advanced Aquarist, 2004.
Moore, Morgan. "Photosynthetic Gorgonians for the Home Aquaria." Reefbuilders, 2013.
Messing, Charles G. et al. "South Florida Ocotocorals: A Guide to Identification."