The Duncanopsammia axifuga, commonly known as the Duncan or Whisker Coral, is a large polyp stony (LPS) coral originating from the Indo-Pacific. This species features striking, fleshy polyps with long, flowing tentacles that create beautiful movement within a tank. The Duncan coral is particularly sought after because it exhibits relatively moderate care requirements compared to many other LPS corals, making it an excellent choice for a wide range of hobbyists. Achieving a thriving, fast-growing colony requires attention to specific environmental parameters, proper placement, and a consistent feeding regimen.
Essential Environmental Parameters
Maintaining a stable water chemistry is the foundation for the health and skeletal growth of the Duncan coral. Temperature fluctuations must be avoided, with an ideal range kept between 75 and 80 degrees Fahrenheit (24–27°C). Consistent salinity is equally important, requiring a specific gravity (SG) of 1.024 to 1.026.
Alkalinity, a measure of carbonate hardness (dKH), should be maintained between 8 and 11 dKH to stabilize the pH and support calcification. Calcium levels should remain between 400 and 450 parts per million (ppm) to provide the building blocks for the skeleton. Magnesium should be kept between 1250 and 1500 ppm for optimal balance.
Beyond these major elements, nutrient control is necessary. The Duncan coral prefers slightly elevated levels compared to some other stony corals. Maintaining nitrates in the 5 to 15 ppm range and phosphates between 0.03 and 0.1 ppm can encourage a stronger feeding response and richer coloration.
Placement and Lighting Requirements
The physical placement of the Duncan coral in the aquarium influences both the light intensity and water movement it receives. This species is classified as a moderate-light coral, thriving in a photosynthetically active radiation (PAR) range typically between 100 and 150 PAR. This means the coral is best placed in the lower to middle regions of the tank, where it receives sufficient energy without being overwhelmed.
When first introducing a Duncan coral, place it lower in the tank and gradually move it up over several weeks to allow for acclimation. Sudden exposure to intense light can cause stress, leading to polyp retraction or bleaching. The coral should be mounted securely to a stable rock structure or placed directly on the sand bed, ensuring it has ample space to expand its colony without touching other corals.
Water flow requires a low to moderate, indirect current. The goal is to provide enough flow to gently sway the polyps and prevent detritus from settling on the tissue. However, the flow must not be so strong or direct that it prevents the polyps from fully extending or capturing food, which can lead to tissue damage and retraction.
Feeding and Nutritional Support
The Duncan coral employs a dual feeding strategy, relying on energy produced by its symbiotic algae (zooxanthellae) and the direct capture of food from the water column. While the algae provide a significant portion of the coral’s nutritional needs, active target feeding is necessary to achieve the fastest growth rates and largest polyp size. The polyps are often extended during the day, making them receptive to feeding at almost any time.
Specific food types that Duncans readily accept include meaty items like mysis shrimp, brine shrimp, and finely minced prepared seafood. These foods should be delivered directly to the individual polyps using a pipette or feeding baster to ensure the coral captures the meal. For optimal health and growth, target feeding should be performed two to three times per week.
The coral benefits from the overall nutritional quality of the water, which includes dissolved organic compounds and trace elements. While major elements are maintained through dosing or regular water changes, supplements like amino acids or liquid coral foods can support tissue health and coloration. Regular replenishment of trace elements through routine partial water changes ensures the coral has access to necessary nutrients.
Encouraging Growth and Fragmentation
Under optimal conditions, the Duncan coral is considered a medium to fast-growing species, expanding its colony by developing new polyps, or “heads,” that branch out from the base. With consistent parameters and regular target feeding, a healthy colony can produce new heads every three to six months. This branching growth pattern makes the Duncan coral an excellent candidate for propagation, a process known as fragmentation or “fragging.”
To propagate the colony, new heads can be safely removed by cutting the skeletal stalk that connects the new polyp to the main colony. The cut must be made cleanly through the hard, dead skeleton using a tool such as bone cutters or a diamond wheel saw. The cutting should be done underwater to minimize stress and prevent the coral from sliming excessively.
After the new polyp is separated, both the mother colony and the frag should be dipped in an iodine-based solution or a coral dip to cleanse the cut site and prevent potential infection. The resulting frag can then be securely mounted to a small plug or rock rubble with coral glue, allowing it to heal and establish itself as a new, independent colony.