Horn Hard Coral Hydnophora Sp

Horn Hard Coral (Hydnophora sp.)

(Also known as Horn Coral, Branching Horn Coral, or Knob Coral)

Overview

The Horn Hard Coral (Hydnophora sp.) is a striking small-polyp stony (SPS) coral, instantly recognisable by its horn-like branches and distinctive, raised polyp ridges that create a textured, sculptural appearance. Typically bright green, yellow-green, or teal, this coral exhibits intense fluorescence under blue or actinic lighting. While hardy and fast-growing under stable conditions, Hydnophora is highly aggressive toward nearby corals and requires thoughtful placement. Its branching or encrusting growth patterns make it a bold, architectural addition to established reef aquariums.

Origin

Native to the Indo-Pacific region, including the Great Barrier Reef, Coral Sea, Fiji, Tonga, Indonesia, and the Red Sea. Found in shallow reef slopes and outer reef crests, where it receives strong light and vigorous water movement.

Feeding

The Horn Coral is photosynthetic, deriving most of its energy from zooxanthellae living within its tissue. It also benefits from supplemental feeding to boost growth and colouration. Feed 1–2 times per week with:

• Microplankton or marine snow
• Finely powdered coral foods
• Phytoplankton or SPS-targeted coral blends

Feed during periods of moderate flow so fine foods can settle gently over the coral surface.

Lighting

Moderate to high lighting.Hydnophora thrives in bright light conditions provided by LED, T5, or metal halidesystems.

• PAR range: 200–350 ¬µmol/m¬≤/s
• Gradually acclimate to intense lighting to prevent bleaching.
• Blue-spectrum lighting enhances fluorescence and contrast along the polyp ridges.

Water Flow

Moderate to strong, turbulent flow. This coral benefits from alternating current patterns that keep surfaces clean and encourage polyp extension. Avoid direct, laminar jets that could cause tissue erosion.

Placement

• Place on mid to upper rockwork where it receives strong, indirect light and good flow.
• Provide 15–20 cm (6–8 inches) of space from neighbouring corals — Hydnophora is extremely aggressive and will extend long, stinging sweeper tentacles that can kill nearby species.
• Ensure rockwork is secure, as rapid encrusting growth can attach firmly to surfaces.

Tank Mates

Reef safe with caution. Compatible with:

• Peaceful reef fish (clownfish, tangs, gobies, wrasses, etc.)
• Invertebrates such as snails, shrimp, and hermit crabs
• Other SPS corals at a safe distance

Avoid:

• LPS or soft corals nearby (they will be stung and damaged)
• Aggressive or stinging species in close proximity (e.g., Galaxea, Euphyllia)
• Large angelfish or butterflyfish that may pick at coral tissue

Aggression

Highly aggressive.Hydnophora possesses powerful stinging tentacles and can cause severe tissue necrosis in nearby corals. Keep it isolated or in a dedicated section of the reefscape.

Experience Level

Intermediate to advanced. The Horn Coral is durable and fast-growing but requires stable water chemistry and careful spatial management due to its aggression. Suitable for aquarists experienced with SPS or mixed coral systems.

Water Parameters

• Temperature: 24–27°C (75–81°F)
• pH: 8.1–8.4
• Salinity: 1.024–1.026 SG
• Alkalinity (dKH): 8–12
• Calcium: 400–450 ppm
• Magnesium: 1250–1350 ppm
• Nitrate: <5 ppm
• Phosphate: <0.03 ppm
• Tank Size: Minimum 150 litres (40 gallons); larger systems preferred for stable chemistry and spacing

Stable calcium, alkalinity, and nutrient levels are critical for skeletal strength and vibrant colouration.

Reef Compatibility

Reef safe with caution. The Horn Hard Coral adds dramatic shape and fluorescence to SPS or mixed reefs but must be placed with ample space to prevent damage to nearby species. Its aggressive nature makes it best suited as a solitary showpiece coral in the upper reef structure, where it can grow freely and display its natural brilliance