Duncan Coral (Duncanopsammia axifuga): Ultimate Care Guide


The Duncan Coral (Duncanopsammia axifuga) is a welcome addition to any salt-water home aquarium.  Native to Australia and the South China Sea, Duncan Coral usually settle on a reef or bed in deep, slow-moving water.  They live in branching or clustered colonies about 100 feet below the surface.  Sometimes Duncan Coral is also called Whisker Coral or Duncanops Coral, but reef aquarium hobbyists typically call them Duncans. 

Duncan Coral is known for its disc-shaped head and short tentacles, both of which can retract into its tubular body.  The polyp or head ranges from muted brown to vibrant green, but some variants will show a pink or cream color.  The tentacles tend to be darker than the heads and have more variation in their colors, often displaying pink, purple, or red.  Duncan Coral is a Large Polyp Stony (LPS) coral, meaning it has large, fleshy polyps over a calcium carbonate stone skeleton. 

Duncan Coral has a symbiotic relationship with zooxanthellae, single-celled algae capable of photosynthesis.  The zooxanthellae provide energy in return for carbon dioxide and access to sunlight.  However, the Duncan Coral sometimes feeds.  The head has a central mouth, and the tentacles will drag food towards the mouth for consumption.  Although their tentacles are covered with stinging cells called nematocysts, Duncan Corals are not dangerous or aggressive to humans or tankmates.

Duncan Coral is known to have lived in the wild for more than a century, while some hobbyists say that they have kept Duncans for several decades.  Provided that they are not damaged by strong currents or other accidental impacts, Duncan Coral can be hardy and long-lived.       

Duncan Coral (Duncanopsammia axifuga)
Duncan Coral (Duncanopsammia axifuga)

Caring for Your Duncan Coral

Duncan Coral may be one of the best corals for beginners looking to start their first reef aquarium.  The water and placement requirements are not difficult to maintain, and Duncan Coral is compatible with any other non-aggressive tankmate.  Duncans react well to standard lighting setups and food, both of which can be acquired at a modest expense, making it very cost-effective for the aspiring hobbyist. 

Since the Duncan Coral is strikingly beautiful to look at and can be so easy to maintain and care for, it is understandable why it has become so popular among hobbyists in recent years.  Nevertheless, it is necessary to understand all the requirements for maintaining Duncan Coral.  Although it may be easier to care for Duncan Coral than many other corals, it is still a delicate organism and can be damaged by mistreatment or accident.  But if you take the time to plan your aquarium setup, Duncan Coral can be a wonderful addition to your reef for many years.   

Water Parameters

Duncan Coral will thrive in saltwater parameters that are very common for tropical aquariums.  That said, as an LPS coral, it will consume a great deal of calcium and magnesium to build its skeleton, so these specific parameters need to be monitored diligently if you want to maximize the growth of your coral.  Duncan Coral needs a calcium content between 400 – 450 ppm, while magnesium should be between 1250 – 1350 ppm.  Aside from periodic supplementation of magnesium and calcium, there are no special additives required for Duncan Coral.

Duncan Coral will do very well in water that is 72 – 78° F with a pH between 8.1 – 8.4.  It also prefers a dKH between 8 – 12 and SG between 1.023 – 1.025.  Duncan Coral can be very forgiving with water parameters; however, if you want them to grow, thrive, and show the most vibrant colors possible, keep an eye on all these water parameters.

Placement

It’s always best for each aquarium dweller to reproduce their natural habitat as closely as possible.  Duncan Coral prefers to live roughly 100 feet below the surface on rocky reefs or soft sand, so they are well suited to placement in the substrate and low or middle shelf rocks.  Most hobbyists place their Duncan Coral on low-lying rocks, though some keep them in the middle if their aquarium is particularly large.  Wherever you decide to place your Duncan Coral, you will need to coordinate your water flow and light with your placement to ensure those parameters are dialed in properly. 

Water Flow

Duncan Coral prefers slow to moderate water flow reminiscent of the calm waters of Australian reefs where it evolved.  Although some hobbyists praise Duncan Coral for its hardiness and keep it in an aquarium with wavemakers and higher-powered pumps, the tentacles can be damaged in fast-moving water.  Indeed, the skeleton of a large colony can be cracked by fast-moving water as well, so most people put their Duncan Coral in just enough current to set the tentacles swaying lazily.

Although a faster flow can damage your Duncan Coral, you don’t want to keep it in stagnant water.  Duncan Coral will absorb nutrients from the water, and if there is not a sufficient flow, the water around them will become depleted and the coral will suffer.  Make sure you keep enough water moving to satisfy the nutrient demands of your Duncan Coral.  

Tank Lighting

Duncan Coral prefers low to moderate full-spectrum light between 100 – 150 PAR, although there is no consensus among hobbyists and some prefer amounts over 200 PAR.  Duncan Coral is quite forgiving, and it does not seem that light outside the recommended range is guaranteed to stunt its growth or do damage.  Whatever PAR you decide to go with, monitor the behavior and health of the Duncan Coral closely for a few days to look for improvements or any degradation.

When you change the frequency of the light in your tank, it is common for the Duncan Coral to shrivel up, pulling their polyps and tentacles back inside the tube.  Many novice hobbyists believe this means that their Duncan Coral is not getting enough light or that their setup is delivering the wrong frequency.  Strictly speaking, this may not be a reaction by the coral to the change in the light. 

Zooxanthellae algae will recoil when exposed to a change in the light source.  For a time, the algae will cease to photosynthesize, and this will send a shock through the now starving Duncan Coral.  After a day or so, the algae will naturally adjust their chemistry, including their color, so they can resume photosynthesis.  At that point, the Duncan Coral will start receiving its nutrients again from the algae and will reemerge from its protective posture with a new color.

Duncan Coral appears to change colors when exposed to different light sources revealing a range of vibrant reds, blues, greens, and pinks.  After an initial shock, if all other needs are met, the coral should return to its normal behavior after a day or so.  If you are going to experiment with the lights in your aquarium, make sure that all other parameters are fine and closely monitor your Duncan Coral to make sure it does not remain under stress for too long.

Feeding Your Duncan Coral

Duncan Coral gets most of its nutrient intake through the photosynthesis of its zooxanthellae algae; however, most hobbyists feel that a supplementary diet is necessary for optimal health, growth, and coloration.  Even if Duncan Coral does not technically need extra food, it is considered best practice to feed it frozen or live coral foods if you want to maximize its health and longevity. 

Duncan Coral should be fed normal coral foods such as frozen or live Mysis, Brine Shrimp, or Nauplii larvae.  These foods are generally inexpensive and can be found online or at many local pet stores and aquarium shops.  Since these foods are useful for feeding other corals and fish, they work well for targeted feeding and community feeding.  As LPS coral, Duncans can also eat slightly larger food such as finely chopped shellfish and similar types of meat.  Finally, there are specific pellets made for LPS coral that some hobbyists prefer.

Duncan Coral should be fed 2 or 3 times per week to make sure they get all the nutrition they need to thrive.  For targeted feedings, make sure that the food reaches the tentacles, which will then pull the food to the mouth.  If you want to feed your Duncan Coral as part of a community feed, make sure the water is circulating and will carry the food towards the coral.  Otherwise, the other residents of the tank may consume it all before the Duncan Coral can get any.

Duncan Coral will not overeat to the point of damaging itself; however, overfeeding can have unintended consequences.  Overfeeding will cause your Duncan Coral to produce more waste, which it ejects through the mouth.  While this is natural waste production, it will require more frequent cleaning than a reasonable diet.  Also, the food that your Duncan Coral rejects may pollute the water in the tank and degrade the health of all the residents.  Finally, if fish start to consume the food before it starts to pollute the water, they may begin to look at the Duncan Coral as a reliable food source and injure it while rooting around for more scraps.   

Advantages to a Supplementary Diet

Duncan Coral benefit greatly from a supplemental diet.  Hobbyists recommend it so the coral will look its best with clear, vibrant shows of color.  If the Duncan Coral has all the nutrients it needs, it will be less stressed and behave better, keeping its polyps and tentacles out of the tube where you can watch them.  Finally, extra nutrition will greatly increase growth and colonization for the Duncan Coral.

Size and Growth Rate

Duncan Coral will grow a stalk that is several inches tall, a center disk that is about 1” in diameter, and tentacles between .5 – 1”.  If enough nutrition and space are available, new polyps will sprout from the side of the stalk, making the Duncan Coral bush-like in appearance.  In principle, there is no limit to the size of a colony, provided the tank, food supply, and mineral content of the water can support continued growth.   

Duncan Coral grows much faster than many other LPS corals.  Once an individual frag is full-sized, it will sprout an additional polyp about every month or so and may have a full colony in about a year.  As it grows, be sure to continue monitoring calcium levels in the water to maintain its growth rate and skeletal density.  Duncan Coral will achieve its maximum growth rate when its water flow, lighting, and nutrition are all maintained at the appropriate levels.      

Fragging

Duncan Coral reproduces by separating a frag from the colony.  This frag of one or more polyps then grows its own colony nearby.  Duncan Coral can be fragged using a Dremel or bone shears.  In fragging, Duncan Coral is removed from its aquarium and inspected to find a suitable place to cut.  The easiest cut to make is where one or more polyps branch off from the main stalk.  It may be difficult to angle the blade of a Dremel properly, but a power tool is easier than traditional bone shears most of the time. 

After one or more frags are cut off the colony, some prefer to coat the area of the cut with a disinfectant to prevent contamination.  Iodine is an excellent choice but should not be spread on uninjured parts of the coral if it can be avoided.

Many hobbyists prefer to attach the new frag to a rock or disk using aquatic glue.  A Duncan Coral frag should be anchored to its new spot.  If it does not attach properly to the surface, it may fall over when it reaches a larger size and the injuries from such a fall could become infected.  After a few minutes in a coral dip, the original colony and frags are placed back in the aquarium.  The polyps and tentacles, which usually retract during the stressful fragging process, will typically start to reappear within a few hours.    

Although the fragging may seem like a daunting process to new aquarists, veterans say Duncan Coral is very straightforward in this regard.  Duncan Coral frags will grow into healthy new colonies very quickly in the same favorable water parameters, light, and food sources as the original colony.  As with the original, the new colonies should start producing at least one polyp each month after they settle into their new home.  Duncan Coral may be the best on the market to teach new hobbyists how to frag coral successfully.   

Common Problems for Duncan Coral

The most common problem that people have with their Duncan Coral is that the polyps and tentacles stay retracted.  The second most common is that it bleaches; that is, it expels the zooxanthellae that lend it its color, leaving it a sickly white.  Both problems are almost always caused by some sort of stress. 

In an aquarium, most stressors that aggravate corals come from the water parameters and the tank setup.  If your Duncan Coral bleaches or closes, check the water parameters, lighting, and flow to see which one is off.  Maybe the pH is too low, or you need to move it closer to the bottom, away from a strong current.  Perhaps the light is not strong enough, or there are not enough minerals like calcium and magnesium.  Whatever the problem, it is most likely the current, light, or a water parameter that is stressing out your Duncan Coral. 

If everything checks out, make sure the Duncan Coral is not too close to an aggressive coral with sweeper tentacles, as it may be getting attacked.  Fish may also be the culprit if they are nibbling at it to find food.  If necessary, remove the Duncan Coral to a separate aquarium where you can control all the variables. 

Duncan Coral can get a bacterial infection just like any other coral.  This is usually due to an intrusion into the aquarium from outside, like the addition of a new coral.  If you keep your filtration system well maintained and make sure to decontaminate any new arrivals in a coral dip for 5 minutes before adding them, you can save yourself a lot of grief.  Coral dip solutions can be found at any aquatic specialty store or online.

Duncan Coral and Brown Jelly Disease

Duncan Coral can be infected with Brown Jelly Disease just like other LPS corals.  The disease got its name from the brown jelly-like substance that forms on the coral and contains various bacteria, protozoans, and dead coral tissue. 

The cause of Brown Jelly Disease is unknown, and it does not seem to exist in the wild; however, it is highly contagious and very deadly for aquarium corals.  Unfortunately, there is no certain cure for Brown Jelly Disease, so the most important measure is to remove any infected coral immediately from the aquarium without spreading the jelly all over your tank.

If your Duncan Coral contracts Brown Jelly Disease, remove it from the tank and place it in a separate container of tank water.  There is no consensus among hobbyists on the best way to treat the infected coral, but the most common opinion is to remove as much of the jelly as possible, frag the infected polyps, and discard them; it is not worth risking a large outbreak among your other corals.  Take the remaining Duncan Coral and give it an iodine dip for 20-30 minutes, then place it in a quarantine tank for several weeks under close observation.

Duncan Coral is just as susceptible to Brown Jelly Disease as any other coral in your aquarium.  If there are any signs of Brown Jelly in your tank, you must act quickly to mitigate the spread.  Hopefully, after removing the infected polyps, you will be able to return your Duncan Coral to its home.

Purchasing Duncan Coral

Duncan Coral is affordable and easy to find online and at local aquarium specialty stores; you can expect to pay between $10 – $15 for a single polyp frag on average.  Considering the reasonable price and ease of care, Duncan Coral may be the best value for a hobbyist purchasing their first coral frag. 

Why Choose Duncan Coral?

Duncan Coral is an attractive, hardy LPS coral that thrives in a standard tropical salt-water tank.  It prefers medium flow and medium light, making it versatile in its placement within an aquarium.  Duncan Coral eats common LPS coral foods but also relies on photosynthesis for 90% of its nutrition.  In well-maintained conditions, Duncan Coral colonies grow quickly and have a straightforward fragging process, making them quick and easy to cultivate.  On balance, Duncan Coral may be the best beginner coral on the market.   

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With decades of collective fishkeeping experience, we are happy to share the fish care tips that we've picked up along the way. Our goal at Fish Laboratory is to keep publishing accurate content to help fishkeepers keep their fish and aquarium healthy.

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