Hydnophora

Hydnophora, or Horn coral, is a distinctive SPS genus recognisable by the small, horn-like projections (hydnophores) covering its surface. It grows in encrusting, massive, and branching forms, adding unique texture to a reef tank. Maintain calcium at 400–440 ppm, alkalinity at 7.5–9 dKH, and temperature between 25–27°C. Hydnophora are moderately hardy and adapt to a range of conditions, but they have one critical characteristic that demands careful planning — they are highly aggressive.

Place Hydnophora in the mid to upper tank with strong light (PAR 200–400) and high, turbulent flow. The most important consideration is spacing. Hydnophora extend potent sweeper tentacles at night that can reach 10–15 cm and will sting and kill neighbouring corals. Give them a generous buffer zone on all sides, or place them on an isolated rock island where they cannot reach other colonies. This aggressive nature means Hydnophora are best suited to larger tanks where adequate spacing is possible.

Hydnophora are found throughout the Indo-Pacific including Australian waters, and aquacultured specimens are occasionally available from local coral farmers. Fragging requires a bandsaw or bone cutters due to their dense skeleton — wear gloves as the horn-like projections can be sharp. Despite their aggression toward neighbours, Hydnophora are otherwise straightforward to maintain and grow at a moderate pace. They make a bold statement piece in an SPS-dominant system where their space requirements can be accommodated.