Rigid Branching Hydnophora Care Guide
Rigid Branching Hydnophora (Hydnophora rigida) is a LPS coral. Care covers 100-200 PAR, medium-high flow, reef parameters and feeding; intermediate level.
Compiled by Aquairi from published sources · Published · Updated
Overview
Rigid Branching Hydnophora (Hydnophora rigida) is a LPS coral in the family Merulinidae. Branching Hydnophora with thick stalks. Often considered LPS-SPS hybrid; aggressive sweepers.
Taxonomy
- Family: Merulinidae
- Genus: Hydnophora
- Scientific name: Hydnophora rigida
- Common synonyms: Branching Horn Coral
Habitat
In the wild, Hydnophora rigida is reported from Indo-Pacific, where it occupies mid to lower reef slopes and lagoons (typically 5-30 m). The species adopts a branching growth form on hard substrate within zooxanthellate reef communities.
Tank requirements
- Salinity (specific gravity): 1.024-1.026
- Temperature: 24-26 °C (75-79 °F)
- pH: 8.1-8.4
- Carbonate hardness (dKH): 8-11
- Calcium: 400-450 ppm
- Magnesium: 1280-1350 ppm
- Phosphate (max): 0.03 ppm
- Nitrate (max): 5 ppm
- Minimum system age: 3 months
Placement and lighting
- PAR (placement zone): 100-200 PAR
- Water flow: medium-high
Mount this LPS coral on the lower or mid rockwork or on the sand bed (for free-living forms) where light is moderate. Strong direct flow can damage the fleshy tissue; aim for indirect, varied movement.
Feeding
Hydnophora rigida hosts symbiotic zooxanthellae and derives most of its energy through photosynthesis. Additional feeding is generally not required when lighting is adequate.
Compatibility
This coral is very-aggressive toward neighbours. It extends sweeper tentacles capable of stinging adjacent corals, so leave generous spacing (10-20 cm) between colonies. Reef-safe with most fish and invertebrates.
Care notes
Difficulty level: intermediate. Reported skeletal growth in well-tuned reef tanks is approximately 0.3-0.7 cm/month. Propagation by fragmentation is straightforward for branching colonies — separate branches or polyps with a bone cutter, glue to plug, allow 1-2 weeks for healing. Maintain stable alkalinity (avoid swings above ±0.5 dKH per day) to preserve tissue health.
Hydnophora rigida Propagation Guide
Overview
Hydnophora rigida is a large-polyp stony coral in the family Merulinidae. Among the genus it is the thin, openly branching form, and aquarists describe it as a fast-growing, hardy species under appropriate conditions. Its branching skeleton makes it one of the more straightforward Hydnophora to divide.
Reproductive Mode
Stony corals of this group reproduce sexually through spawning and asexually through fragmentation and budding. In the aquarium, propagation relies almost entirely on the asexual route: pieces of the colony detached from the parent regrow into independent colonies.
Fragging / Asexual Propagation
Because the colony grows as discrete branches, propagation is done by cutting individual branch tips away from the main structure. A diamond-tipped cutting tool produces a cleaner cut than plier-style nippers, which speeds healing and lowers the chance of infection at the wound. The detached branch is then mounted on a plug or rock.
- Select healthy branches with good polyp extension and full coloration.
- Cut the branch cleanly with a diamond blade or coral saw.
- Mount the frag and allow the cut surface to heal.
- Dip the frag in an iodine-based coral dip to discourage infection.
Conditions for Propagation
Stable reef parameters and medium to medium-high light and flow support recovery of fresh cuts. Clean, low-stress water and steady alkalinity help the wound seal and the branch resume growth.
Common Challenges
The main difficulty is placement rather than survival. Hydnophora is aggressive toward neighbors: it deploys mesenterial filaments carrying digestive enzymes, and aquarists report sweeper tentacles that can extend several inches and damage corals within a few inches of the colony. Frags need their own clear space well away from other corals.