Open Brain Coral (Trachyphyllia geoffroyi) Propagation Guide
Why Trachyphyllia geoffroyi, the free-living open brain coral, is not routinely fragged: a solitary fleshy polyp that reproduces sexually on the reef rather than by conventional fragmentation.
Overview
Trachyphyllia geoffroyi, the open brain coral, is a large-polyped stony coral in the family Merulinidae. It is a free-living species that sits unattached on sandy substrates, sandy reef slopes, and lagoons across the Indo-Pacific, and inflates a very fleshy mantle by day that extends beyond the skeleton and retracts when disturbed. It rarely exceeds about 20 cm in diameter and grows in a flabello-meandroid form.
Reproductive Mode
Unlike branching LPS, the open brain is essentially a single, free-living polyp (sometimes with a few mouths in the valley region) and is not suited to conventional fragging. Reef Builders groups single-polyp LPS such as scolys, meat corals, and fungias as corals that are not conducive to conventional fragging techniques; the open brain belongs to the same category, so it is not routinely fragmented.
Fragging / Asexual Propagation
- Conventional branch-separation fragging does not apply, because there are no separate heads on branches to divide.
- Asexual increase occurs mainly through natural budding of the polyp over time, not deliberate cutting.
- Cutting through the single fleshy polyp is possible but uncommon and risky, and is treated as an advanced technique rather than standard practice.
- For most aquarists, the practical approach is to keep the coral healthy rather than to propagate it.
Because each specimen is one large polyp, dividing it means cutting through living tissue and the skeleton together, which is far riskier than separating branches on a phaceloid coral.
Conditions for Propagation
Keep temperature near 24-26 degrees Celsius and pH 8.1-8.4 with stable alkalinity, calcium, and magnesium. The coral sits on the sandbed in low flow and medium light; gentle handling and spot feeding support recovery if a polyp is ever divided.
Sexual Reproduction
On the reef, Trachyphyllia geoffroyi reproduces sexually. The genus is heavily collected for the aquarium trade, with over 60,000 specimens reported exported from Indonesia in 2005, and the IUCN lists it as Near Threatened, underscoring that wild collection rather than captive propagation supplies most specimens.
Common Challenges
The fleshy mantle is easily damaged by sharp rock or strong flow and can tear, opening the door to infection. Because the coral is not readily fraggable, attempts to divide a single polyp risk losing the whole animal, so propagation is not recommended for typical aquarium keeping.