Duncan Coral

Overview

Appearance: Each round polyp has a central mouth surrounded by long tapered tentacles. When expanded, the tissue can hide much of the branching skeleton.

Notable Characteristics: Large daily polyp expansion, strong feeding response, visible branching growth, relatively mild aggression, and good tolerance compared with many LPS corals.

Natural Habitat

Native Distribution: Recorded primarily from Australian waters and adjacent western Pacific regions.

Natural Reef Habitat: Protected reef slopes, sandy or rubble areas near hard substrate, and deeper or turbid reef environments.

Depth: Often found in deeper or lower-light reef zones, though exact depth varies by location.

Natural Lighting: Low to moderate natural light, frequently reduced by depth or turbidity.

Natural Flow: Gentle to moderate water movement that delivers plankton without battering expanded tissue.

Other Habitat Notes: Colonies may occur where suspended food is available and sediment does not remain on the polyps.

Aquarium Placement

Recommended Placement: Lower to middle rockwork or a stable ledge with low-to-moderate indirect flow and room above and around the colony.

Space Requirements: Allow at least 3-6 inches from nearby corals as a starting separation, with enough vertical room for the polyps to expand fully. Set clearance from the expanded colony, observed reach (including after dark), current direction, neighboring aggression and future growth; allow greater distance from aggressive LPS corals with long sweepers. No fixed distance guarantees separation; reassess for contact.

Rock/Sand Placement: Secure the skeleton to stable rock. Sand placement is acceptable only if the colony cannot tip, become buried, or abrade its tissue.

Attachment Method: Use cyanoacrylate gel or reef-safe epoxy on exposed dead skeleton or the frag plug; never cover living tissue.

Orientation: Keep corallites upright or gently angled so food and debris do not collect in the mouths and tissue does not rub rock.

Other Placement Notes: Account for expansion before choosing a crevice. Tissue rubbing against sharp rock can lead to recession.

Lighting

Lighting Requirement: Low to moderate; strong light is unnecessary and can cause retraction or bleaching without acclimation.

PAR Range: Approximately 50-150 PAR; start around 75-125 PAR and adjust gradually to extension and coloration.

Spectrum Considerations: A balanced reef spectrum with blue and violet wavelengths supports photosynthesis and fluorescence.

Acclimation Requirements: Begin in lower light and increase exposure over one to several weeks after shipping or a major fixture change.

Signs of Too Much Light: Persistent retraction, pale or washed color, bleaching, shortened extension, or tissue recession on the light-facing side.

Signs of Too Little Light: Dull or browned coloration, stretching, weak skeletal growth, and reduced budding despite otherwise suitable conditions.

Water Flow

Flow Requirement: Low to moderate indirect flow that gently moves the tentacles and keeps debris suspended.

Preferred Flow Pattern: Broad, random, or alternating movement rather than a constant direct jet.

Signs of Excessive Flow: Tentacles remain pinned to one side, polyps cannot open, tissue pulls against the skeleton, or recession develops.

Signs of Insufficient Flow: Detritus and mucus collect between heads, food remains on tissue, or extension and gas exchange decline.

Water Parameters

Temperature: 75-80°F (24-27°C)

Salinity: 1.024-1.026 specific gravity (about 32-35 ppt)

pH: 8.1-8.4

Alkalinity: 8-11 dKH, maintained consistently

Calcium: 400-450 ppm

Magnesium: 1250-1400 ppm

Nitrate: Approximately 2-15 ppm; avoid both abrupt nutrient starvation and chronically excessive levels

Phosphate: Approximately 0.03-0.10 ppm; stable measurable phosphate is often preferable to zero

Other Relevant Parameters: Ammonia and nitrite should remain at 0 ppm. Maintain good gas exchange and appropriate potassium and trace elements through regular saltwater maintenance rather than blind dosing.

Parameter Sensitivity: Moderately tolerant, but sudden changes in salinity, temperature, alkalinity, light, or nutrients can trigger prolonged retraction or tissue loss.

Stability Requirements: Stable alkalinity and salinity are especially important for skeletal growth; make corrections gradually.

Feeding & Nutrition

Photosynthetic: Yes. Symbiotic dinoflagellates provide much of its energy under suitable lighting.

Natural Feeding: Captures zooplankton, suspended organic particles, and small prey with its tentacles.

Target Feeding: Optional but beneficial. Place a small portion near each open mouth with flow reduced briefly and remove uneaten food.

Recommended Foods: Mysis shrimp, enriched brine shrimp, copepods, finely chopped marine flesh, and appropriately sized sinking coral foods.

Feeding Frequency: Once or twice weekly is sufficient for most colonies; avoid feeding oversized pieces or every day.

Benefits of Feeding: Can support faster budding, fuller tissue, recovery, and growth in lower-light or nutrient-poor systems.

Special Nutritional Requirements: No special supplement beyond stable calcium, alkalinity, magnesium, balanced nutrients, and appropriately sized food when target feeding.

Growth

Growth Rate: Moderate, with faster head production possible under stable chemistry and regular modest feeding.

Growth Pattern: New daughter heads bud from the sides or base of existing corallites, gradually forming a branching colony.

Maximum Colony Size: Can develop into a large multiheaded colony over several years; practical size depends on available space and fragging.

Space Requirements: Leave room for branches, full polyp inflation, and access for cleaning or fragging.

Overgrowth Concerns: It does not normally encrust aggressively, but an expanding colony can shade neighbors or press tissue against nearby rock and corals.

Aggression

Aggression Level: Low to moderate for an LPS coral.

Sweeper Tentacles: Usually absent or short compared with many aggressive LPS corals; normal tentacles can still sting on contact.

Chemical Warfare: Limited compared with many soft corals, but mucus and dissolved compounds contribute to mixed-reef competition; carbon and water changes can help.

Stinging Ability: Mild to moderate on direct contact and generally limited to the reach of expanded polyps.

Required Spacing: Provide 3-6 inches and additional distance from corals with long sweeper tentacles.

Corals to Avoid Nearby: Keep beyond reach of Euphyllia, Galaxea, bubble corals, chalices, and other strongly stinging LPS corals.

Compatibility

Fish Compatibility: Compatible with most reef-safe fish; butterflyfish, large angelfish, filefish, and other coral pickers may nip fleshy polyps.

Invertebrate Compatibility: Generally compatible with reef-safe shrimp, snails, and crabs, though animals that steal food or walk repeatedly over the colony can irritate it.

Coral Compatibility: Works well in mixed reefs when spacing prevents direct contact and aggressive neighbors cannot reach it.

Potential Predators: Coral-nipping fish, some nudibranchs, and other LPS predators may consume or damage tissue.

Potential Irritants: Vermetid mucus, sediment, food-stealing shrimp, crabs, algae at the skeleton-tissue boundary, and nearby stinging corals.

Fragging & Propagation

Difficulty: Moderate

Propagation Method: Separate one or more healthy heads by cutting the branching skeleton well below the living tissue.

Tools/Method: Use gloves, eye protection, coral bone cutters or a rotary tool, a separate container of aquarium water, and cyanoacrylate gel for mounting. Keep heat, vibration, and debris away from living tissue.

Healing: Return the frag to stable water with moderate light and gentle flow. Polyps may reopen within days, while the cut skeleton takes longer to stabilize and grow.

Special Risks: Cutting too close to tissue can tear the polyp, expose skeleton, or start infection; branching skeleton can splinter sharply.

Safety Considerations: Wear waterproof gloves, eye protection, and respiratory protection when power-cutting dry or aerosol-producing skeleton. Control dust and splashes, disinfect tools, and never cut through inflated living tissue.

Health & Common Problems

Tissue Recession: Often follows unstable alkalinity or salinity, physical injury, excessive flow, a neighboring sting, infection, or chronic nutrient imbalance.

Bleaching: Usually linked to excessive light, overheating, or rapid environmental change. Reduce stress gradually and stabilize the system.

Polyp Retraction: Brief closure after maintenance or feeding is normal. Persistent retraction suggests flow, lighting, chemistry, pests, irritation, or disease.

Pests: Flatworms, nudibranchs, algae, vermetid snails, and other hitchhikers may irritate tissue; inspect, dip appropriately, and quarantine new colonies.

Diseases: Bacterial tissue loss and brown-jelly-like infections can occur after injury or stress and may spread rapidly among heads.

Signs of Stress: Persistent closure, gaping mouths, deflated or peeling tissue, exposed skeleton, brown mucus, bleaching, poor feeding response, or rapid head loss.

Common Keeper Mistakes: Using excessive light or direct flow, allowing tissue to rub rock, feeding oversized food, making abrupt alkalinity changes, and ignoring early tissue recession.

Recovery Considerations: Correct the cause gradually, improve gentle flow, remove trapped debris, separate clearly healthy heads if tissue loss spreads, and quarantine or treat suspected infection promptly.

Beginner Suitability

Beginner Friendly: Yes, for a cycled and stable reef aquarium.

Why: It tolerates moderate conditions, feeds readily, lacks long aggressive sweepers, and gives clear visual feedback through polyp extension.

Major Challenges: Maintaining stable alkalinity and salinity, avoiding excessive flow, recognizing tissue recession early, and preventing food theft.

Before You Buy

Important Considerations: Choose a colony with inflated polyps, intact tissue around each skeleton rim, no brown mucus, no exposed recent recession, and no visible pests.

Space: Allow room for full extension and future daughter heads rather than sizing the location to the contracted frag.

Lighting: Ask about the seller's PAR or placement and acclimate gradually to your system.

Flow: Choose broad low-to-moderate flow that moves tentacles without pinning them.

Aggression: Duncans are relatively peaceful, but must be protected from stronger neighboring stingers.

Parameter Stability: Add only after the aquarium can maintain stable salinity, temperature, calcium, magnesium, and alkalinity.

Long-Term Growth: Plan for a branching multiheaded colony and future fragging access.

Species-Specific Information

Trade-name and care considerations

Duncan Coral was once reported as uncommon in the wild despite becoming widely propagated in aquariums. Individual morphs differ in tentacle length, color, head size, and growth rate. A closed colony is not automatically starving; repeated feeding will not solve unsuitable flow, light, chemistry, or tissue disease.

Evidence and practical scope

Care evidence: Tidal Gardens describes 50-150 PAR and lower indirect flow for its Duncan colonies. Its feeding observations are grower experience, not a guarantee of growth or a reason to dose supplements indiscriminately.