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Hammer Coral
Euphyllia ancora
Animalia›Cnidaria›Anthozoa›Euphylliidae
📍 Indo-Pacific Reef Systems
Hammer coral is a large polyp stony (LPS) coral with distinctive T-shaped or hammer-shaped tentacles that sweep rhythmically in current. It is photosynthetic via its zooxanthellae but also benefits from target feeding with meaty foods two or three times weekly. It can sting neighbouring corals, so adequate spacing is essential.
Tank Mates
Hardy reef fish; may occasionally brush corals but generally compatible with proper spacing
Beneficial invertebrate that removes parasites and debris without damaging coral tissue
Peaceful scavenger that helps maintain water quality and poses no threat to corals
Small, reef-safe fish that stays in lower water column and avoids coral damage
Both are LPS corals; maintain adequate spacing to prevent sweeper tentacle contact
Algae-eating snail that helps maintain tank cleanliness without harming corals
Common Diseases
Coral Bleaching
Loss of color, polyps appear white or translucent, reduced feeding response
Reduce lighting intensity, check water parameters (especially temperature and alkalinity), improve water circulation, maintain stable conditions; may recover if stressor is removed quickly
Brown Jelly Disease
Brown, gelatinous film covering coral tissue, rapid tissue recession, foul odor
Isolate coral if possible, perform 25% water change, increase water flow, remove affected tissue with clean tools, treat with antibiotics or iodine-based dips in severe cases
Polyp Necrosis
Polyps fail to extend, tissue darkening or discoloration, slime coating
Check water parameters (pH, alkalinity, calcium), improve water quality through partial changes, reduce feeding temporarily, ensure moderate indirect flow; may indicate poor water conditions
Parasitic Infection
Visible spots or lesions on polyps, excessive mucus production, reduced polyp extension
Maintain excellent water quality, increase aeration and flow, consider copper-free parasite treatments designed for corals, quarantine if spreading to other corals
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Quick Facts
- diet
- Photosynthetic (zooxanthellae); supplement with mysis shrimp, copepods
- flow
- Moderate, indirect
- lifespan
- Decades in well-maintained reef
- lighting
- Moderate (50–150 PAR)
- placement
- Lower to mid rockwork
- tank size
- 30 gallons minimum reef tank
- temperament
- Has sweeper tentacles; aggressive toward nearby corals
Water it likes
- ph
- 8.1–8.4
- calcium
- 400–450 ppm
- nitrate
- 1–10 ppm
- salinity
- 1.024–1.026 SG
- magnesium
- 1250–1350 ppm
- phosphate
- 0.03–0.1 ppm
- alkalinity
- 8–11 dKH
- temperature
- 73–81°F (23–27°C)