Hammer Coral (Euphyllia ancora)

The Hammer Coral (Euphyllia ancora) is a reef aquarium staple kept for colour, motion, and aquascape structure. This profile matches our other coral and invertebrate guides with origin, lighting, flow, water chemistry, feeding, placement, and husbandry pitfalls.

Keeper notes: Long sweeper tentacles at night — give clearance from other corals. Keep Ca/Alk/Mg stable. Related to torch and frogspawn in care style.

Natural Habitat and Origin

Wild colonies are associated with Indo-Pacific reef slopes and lagoons. Translating that into aquariums means mature rock, stable salinity, and lighting/flow that match the species’ depth preference rather than blasting every coral with identical PAR.

Hammer Coral in aquarium
Hammer Coral (Euphyllia ancora). Photo: Diego Delso / Wikimedia Commons (CC BY-SA 4.0)

Appearance and Colony Form

Typical aquarium size/range: colonies expand; large frags become dinner-plate heads over years. Healthy tissue looks inflated, colourful (or naturally brown with strong fluorescence under actinics), and responsive to light cycle changes. Receding tissue, bleach, or stringy pests deserve immediate chemistry and pest checks.

Close view of Hammer Coral (Euphyllia ancora)
Hammer Coral (Euphyllia ancora). Photo: Diego Delso / Wikimedia Commons (CC BY-SA 4.0)

Lighting and Flow

  • Light: moderate (PAR often mid-range; acclimate slowly)
  • Flow: moderate, indirect — tentacles should sway, not thrash
  • Acclimate new frags by starting lower and raising intensity over 1–2 weeks
  • Observe for closed polyps (too much flow/light) or stretched searching behaviour (too little)

Water Conditions

  • Temperature: 75–80°F (24–27°C)
  • Salinity / SG: 1.024–1.026
  • pH: 8.1–8.4
  • Tank: 30 gallon (110 L)+ reef with stable alkalinity
  • Alkalinity / calcium / magnesium: keep reef parameters stable; avoid big daily Alk swings
Real Reef Canada

Feeding

Ecology: photosynthetic LPS; accepts meaty foods (mysis, reef food). Many photosynthetic corals still benefit from periodic target feeding or broadcast reef foods when nutrient export is strong. Feed lightly — excess nutrients fuel algae.

Placement and Aggression

Give chemical and physical space. LPS sweepers, zoanthid mats, and anemones can wage slow wars across rock. Mount frags on plugs for easy rearranging while they find a permanent home.

Ease of Care

Care level: intermediate. Stability, cleanliness, and patience outperform constant additive tinkering.

Common Problems

  • Bleaching from sudden light intensity changes
  • Tissue recession from Alk crashes or pests
  • Chemical warfare when coral aggression is ignored
  • RTN/STN events after shipping stress or parameter spikes
Hammer Coral natural colour and form
Hammer Coral (Euphyllia ancora). Photo: Les Williams / Wikimedia Commons (CC BY-SA 2.0)

Conclusion

Hammer Coral (Euphyllia ancora) can be a showpiece coral when lighting, flow, and water chemistry stay consistent. Use this guide alongside our other invertebrate and reef profiles for clear, practical long-term care.