Care guide · Marine · corals

Duncan coral

Duncanopsammia axifuga

Species level

Photo: User:Haplochromis · Source · CC BY-SA 3.0Resized and compressed; no cropping or colour changes.

Duncanopsammia axifuga forms a branching colony with conspicuous, flower-like polyps. It can be an appealing first stony coral for an aquarist who already maintains a stable marine aquarium: the polyps respond visibly to food and the colony can gradually produce new heads. Beginner-friendly does not mean suitable for a newly established tank. Fluctuations, a hard pump jet and damage to the soft tissue deserve particular attention. Give a small frag room to grow from the outset and assess the fully expanded colony. This guide covers the named species, rather than every coral that resembles a flower or anemone in the trade. Light, water movement and careful supplementary feeding work together; increasing all three is not automatically better.

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At a glance

Identification level: Species level
Coral group: LPS
Difficulty: Easy
Growth and pruning: Moderate
Temperature: 24–26 °C
Specific gravity (SG at 25 °C): 1.025–1.026 SG
pH: 8.1–8.3
Alkalinity: 8–9 °dKH
Calcium: 400–450 mg/L
Magnesium: 1250–1350 mg/L
Light requirement: Moderate
par: 50–150 µmol/m²/s
Flow requirement: Low to moderate, Moderate
Position: Low, Middle
Aggression: Semi-aggressive
Supplementary feeding: Optional

Water values are reef-care guidance, not proven species limits. PAR describes only the stated culture experience; stability and gradual acclimation remain important.

About this coral

A calcareous skeleton lies beneath the soft tentacles. A retracted polyp can therefore look quite different from a fully expanded animal. Duncanopsammia axifuga belongs to Dendrophylliidae, but should not receive the same care as a non-photosynthetic sun coral merely because the two are related. Its partnership with light-using microalgae is important. A green oral disc, brown tentacles or a trade name for a colour variant does not establish a separate species. When buying, also look for intact tissue around the skeletal heads.

Natural habitat

The natural distribution is Indo-Pacific; many aquarium specimens and cultured lines are associated with Australia. A seller's origin label is not the same as a documented collection locality, however. The branching structure raises polyps above the substrate and allows exchange with passing water. In an aquarium, provide a place where water moves between the heads and debris does not accumulate. Do not translate an assumed natural depth directly into mounting height: clarity, light optics and water colour jointly determine the light actually reaching the animal.

Aquarium and layout

Secure the base to rock or a suitable holder in the lower or middle reef. Living tissue must not rub against a rough edge or become buried in sand. Check clearance with the polyps fully expanded, including when flow bends them sideways. A small frag on a loose plug is vulnerable to a snail pushing against it. Keep the colony accessible for inspection and modest targeted feeding. No defensible species-specific minimum volume has been established; stability, colony size and open space matter more than an arbitrary number of litres.

Water conditions

The central values above are care guidelines for a stable reef, not experimentally established survival limits. Skeletal growth consumes calcium and alkalinity. Measure trends, preferably under comparable conditions, before choosing a supplement. An unexpected result calls first for checking the test, salinity and recent maintenance. Magnesium belongs to that broader chemical balance. Do not blindly pursue undetectable nitrate and phosphate: both shortages and accumulation can be problematic. Hard, universal nutrient limits have not been demonstrated for this species. Abruptly changing an established stable situation to reach an attractive number can itself cause harm.

Lighting and acclimation

This coral generally does not require exceptionally powerful lighting. Culture advice differs: ORA describes more light and flow for its own line than the cautious Tidal Gardens guidance. Ask about the previous conditions of your frag. The stated PAR guidance comes from documented culture experience, not a guaranteed biological boundary. Measure at the polyps; a reading at the centre of a light tells little about a shaded edge. After purchase, start with a less intense position or appropriate dimming and assess the response before increasing exposure. Constant relocation makes that assessment harder. Fading, persistent closure or receding tissue may involve light, but also calls for checking water, flow and possible injury. Extending the photoperiod does not automatically compensate for an unsuitable spectrum.

Water movement

Start with gentle to moderate indirect movement that lets the tentacles move without continually pressing them to one side. Some cultured lines are maintained in stronger flow, so this is not a demonstrated upper limit for the species. Flow should carry waste away and bring oxygen and food. A powerful straight jet onto a skeletal head can damage tissue. Observe the animal rather than relying on the pump label. If debris remains between the heads, a different pump setting or position may help more than increasing total output. Recheck as the colony becomes denser.

Feeding

Alongside the contribution from its symbionts, this coral can take small animal-based food particles. Modest targeted feeding is useful when ingestion is visible; an open polyp is not an invitation to fill its mouth. Let small suitable particles reach the tentacles gently and check that they are swallowed. Stop if the animal remains closed or releases food again. Temporarily reduce local flow if necessary, then restore it. Allow for fish and shrimp stealing food. Additional feeding also increases the load on the water system.

Growth and behaviour

New polyps can develop along the colony, turning an initially open frag into a much denser structure. Growth depends on conditions and feeding; promising a fixed number of new heads each month is not justified. Take occasional photographs from the same angle to distinguish expansion from tissue recession. Space that seems adequate today may later restrict light or circulation. Adapt layout and maintenance to the growing colony without repeatedly injuring it.

Aggression and spacing

Duncan coral is relatively mild compared with strongly combative LPS, but still has stinging tentacles and sensitive living tissue. Do not let neighbouring corals touch it. Check the night-time extension of more aggressive neighbours and consider the direction in which their tentacles move. A fixed safe number of centimetres is not supported. Clearance must develop with both colonies. Damage confined to the edge facing a neighbour is a reason to investigate the contact pattern more closely.

Keeping with fish

Assess fish by their actual behaviour around these fleshy polyps. Individual dwarf angelfish may nip, even after apparently uneventful coexistence. A general reef-safe rating therefore does not guarantee this pairing. Watch during feeding too: a fish trying to retrieve food from a closed polyp can cause damage without being a specialist coral eater. A sand-sifting goby can cover low-placed heads. Use the reviewed species relationships and retain a practical way to separate the animals.

Keeping with corals

Less aggressive LPS may share the aquarium when each has its own suitable light and flow zone. This does not permit the colonies to grow into one another. A torch coral is a poor immediate neighbour because of its long stinging tentacles. Fast-growing soft corals may shade Duncan coral or occupy its open space. In mixed reefs, consider chemical competition and overall water quality too. The relationships below describe conditions for keeping animals together, not a recommendation to crowd all listed corals together.

Other invertebrates

Choose marine invertebrates by species, not merely by the clean-up-crew label. A grazing snail can topple a poorly secured frag; a shrimp that removes food can disrupt targeted feeding. Large or opportunistic crabs are not automatically suitable companions. Look for actual tissue loss and distinguish it from temporary closure as an animal crosses the colony. No universally safe pairing exists for broad groups such as starfish. The freshwater shrimp and snails already in this database are not candidates for this reef.

Propagation and fragging

A healthy branching colony may be propagated by having a well-separated skeletal portion removed. Avoid cutting through living polyps or forcing closely packed heads apart. An injured, recently transported or poorly expanding colony should recover first. Use appropriate protection and clean aquarium tools; coral mucus and sharp skeletal edges require careful handling. Attach at the dead skeleton or holder, rather than applying glue to living tissue. Have an experienced grower assess uncertain cases.

Possible problems

Brief closure after contact differs from deterioration lasting days. With persistent closure, check stability, local flow, lighting, sand accumulation and tankmates in turn. Brown slimy material, rapid tissue loss or newly exposed skeleton calls for prompt assessment and separation where this can be done safely. That appearance alone does not identify a particular pathogen; do not add arbitrary medicines or disinfectants. Record changes and, where possible, adjust one environmental factor at a time. Judge recovery by lasting intact tissue and normal behaviour, not just a briefly inflated polyp.

Keeping with other species

Care products

No sufficiently supported match to a specific existing care product has been established for this coral. Follow the feeding and care chapters; an absent product card does not mean feeding or measurements are unnecessary.

Sources & review

This care guide draws on several specialist sources and was last checked on 9 October 2026.

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