Duncan coral (Duncanopsammia axifuga), also known as branched disc coral, whisker coral or duncanops coral, can be an appealing addition to many reef saltwater aquariums. Originating from Australia, Duncan coral is a community player and a vibrant green and purple addition to any saltwater tank. This species has done well in aquaculture conditions and is readily propagated.
Duncan corals are characterized by their disc-shaped body, and short purple/green tentacles that can quickly retract into their calciferous tube home. Members of the family Dendrophyllidae, they are related to other stony corals such as Astroides spp. and Turbinaria spp. They can be classified as a large-polyp stony coral (LPS) and are common in aquacultured assortments. Since they reside in a stony tube, it is critical to carefully move the entire animal in order to prevent fragmenting their home and/or body. As they get larger, you may see new polyps or heads extending from the sides of the tubes.
These peaceful corals get along well with many other corals and other invertebrates. They do not have any natural defenses that may harm fish, so their tube homes may be nibbled on by aggressive tank mates. Be careful about which fish you add to aquariums with stony corals! Even if fed properly, the fish may not be able to keep themselves from giving your corals a nibble. This is safe for the fish, but may decimate your coral colonies. When in doubt, only keep "reef safe" fish in coral tanks.
Due to their delicate nature, Duncan corals prefer areas of low to moderate water movement. This may be an area in the middle to lower part of your tank, away from outcroppings and peaks with higher water flow, better suited to sturdier corals. With proper care, Duncan corals can easily spread throughout your aquarium, therefore are not well suited to nano tanks, but most larger tanks can accommodate their spread.
How to Care for Your Duncan Coral
Like other corals, Duncan coral contains zooxanthellae symbiotic algae within their tissues that provide most of their food source. In order to function properly, their algae needs adequate lighting. In the coral light spectrum, Duncan corals require low to moderate full spectrum lighting. As with other coral reef tanks, be sure to adapt your light to normal cycles of light and dark. Some specialized lights can even do a slow fade between cycles to mimic "sunrise" and "sunset" or even "moonrise" and "moonset!" These cycles are critical if you are looking to breed fish or invertebrates.
In addition to their photosynthesizing tenants, Duncan corals can benefit from an occasional feeding of small zooplankton. Frozen variety mixes in addition to more meaty foods, such as mysis, aren't a daily requirement, but a few weekly meals will boost your coral's appearance and growth.
Like other stony corals, Duncan corals have trace element requirements in order to keep sturdy homes. Depending on your salt mix, you may need to add in calcium, strontium and other trace elements. Be sure to test these levels regularly, in addition to your other water chemistry tests, to make sure the levels are within range.
As with all live aquatic species, corals can carry bacteria and viruses. Before adding any new corals to an established aquarium, be sure to quarantine them in a separate system, using separate equipment, for a minimum of four weeks. Buy your corals from reputable dealers who use safe propagation techniques and do not take from wild stocks. This will ensure your tank will stay healthy and safe from infection!
Failure to Thrive
Provided that you bought from a good source and quarantined your coral appropriately, the first thing to consider with a coral failing to thrive is water quality. This includes your usual water parameters (ammonia, nitrite, nitrate, pH, kH, gH, temperature and salinity), coral specific parameters (calcium, strontium and other trace elements), and sunlight. Yes, how much sunlight or artificial broad-spectrum lighting your coral gets directly affects its symbiotic zooxanthellae. Duncan corals are on the low to moderate spectrum for coral lighting, so you may have to adjust up or down, depending on your setup.
If all your water quality parameters are within normal range, make sure your coral is in an area of low to moderate water flow and not being harassed by any of their tank mates, fish and other corals alike. Remember, some corals do not play nice with close neighbors and will send a chemical attack their way. Nibbly fish may want to nip at corals no matter how much other food you offer.
If your coral doesn't like where they are placed in your tank, they may decide to make a change themselves! Within their tubular homes, you may see additional tubes forming away from the main body. Take the hint your coral is telling you and be sure to keep them in a more suitable environment. Don't force a coral into an area that doesn't suit them just because it fits your aesthetic!
Algae Growing on Polyps
Many times, this is a problem with too much food for the algae. Test your nitrate and phosphate levels to make sure they are within the correct ranges. Most of the time, this will require a few extra water changes to bring your levels down. Using a small suction device made out of rigid and flexible airline tubing will allow you to carefully clean the algae off of your corals. If you leave the algae on the corals, the zooxanthellae contained within the polyps will not have access to light and your coral will die.
Even if you are using a reef-specific salt mix, your phosphate may still be out of range. It depends on the types of corals you have in your aquarium and how many supplements they require. Soft corals have fewer requirements than hard or stony corals. If you cannot get your phosphate level down, consider trying a different salt mix or adding more stony corals into the aquarium to absorb the phosphate. There are filter media that can be used that absorb phosphate and will lower the level in the water, reducing unwanted algae growth.