Hammer Coral
Euphyllia ancora
Flowing hammer-tipped tentacles that sway in the current — a showpiece LPS.
Difficulty: Beginner–IntermediateLPS coral
The hammer coral (Euphyllia ancora, “anchor coral”) is a flowing, hammer-tipped LPS that sways in the current like a field of tentacles — one of the most popular reef centrepieces. It's forgiving for an LPS: moderate light, gentle flow, and the occasional meaty snack. The one rule is space — its sweeper tentacles sting other corals.
Care at a glance
| Colony / form | A wall or branching skeleton topped with flowing hammer-/anchor-tipped tentacles; grows into a showpiece head by head. |
|---|---|
| Lighting | Low–moderate — about 50–150 PAR. Modest light is fine; stronger light can deepen colour but isn't required. |
| Water flow | Low-to-moderate, gentle and indirect — enough to sway the tentacles, never so strong they retract or tear. |
| Placement | Lower-to-mid rockwork or the sand, in gentle flow — with SPACE: keep non-Euphyllia corals at least ~6 in (15 cm) from its sweeper tentacles. |
| Temperature | 75–82°F (24–28°C). |
| pH | 8.1–8.4. |
| Specific gravity | 1.023–1.026 (reef-standard ≈35 ppt). |
| Other targets | LPS build a stony skeleton — keep alkalinity (≈8–11 dKH), calcium (≈400–450 ppm) and magnesium (≈1300–1450 ppm) stable. More forgiving than SPS, but don't let them swing. |
| Feeding | Mostly photosynthetic; a subdued eater that benefits from the occasional meaty morsel (mysis) but doesn't demand target feeding. |
| Growth & spread | Grows steadily head by head into a showpiece; fragged by experienced keepers (cut the skeleton, not the flesh). |
| Natural range | Indo-Pacific reefs. |
The fish store gets these wrong
Common myths, kindly corrected — no shame for having believed them.
- “LPS need blasting SPS-level flow and light.” No — Euphyllia want LOW-to-moderate, gentle flow and only modest light. Too much flow keeps the tentacles retracted and can tear them.
- “Reef-safe corals won't hurt each other.” Euphyllia are chemically peaceful to fish/inverts, but they extend stinging sweeper tentacles that damage other corals — space is the safeguard.
Before you buy
- Plan a spot with gentle, indirect flow.
- Leave ~6 in of space from non-Euphyllia corals for its sweepers.
- You can group it with frogspawn/anchor; give a torch extra room.
- Be ready to keep alk/Ca/Mg stable (it builds a skeleton).
Signs something's wrong
A struggling coral is almost always telling you about light, flow or water — here's what to watch for:
- Tentacles staying deflated/retracted — usually too much flow, or a swing in alkalinity; ease the flow and check chemistry.
- Receding flesh or exposed skeleton at the base — often an alk/Ca swing, or too much light too fast.
- A brown, jelly-like film spreading over the tentacles (“brown jelly”) — act fast: remove the affected piece, dip it, and improve water quality.
Never
- Never place it in strong, direct flow.
- Never crowd it against other (non-Euphyllia) corals — the sweepers sting.
- Never let alkalinity swing — stability matters for LPS.
Common hammer coral questions
Where should I place a hammer coral, and how much space does it need?
Lower-to-mid rockwork or the sand, in gentle indirect flow. Give it space: keep non-Euphyllia corals at least ~6 inches away, because its sweeper tentacles sting neighbours. You can usually group hammers with frogspawn and anchor corals, but give a torch extra room.
Are hammer corals good beginner corals?
They're one of the best first "big" LPS — hardier and more forgiving than SPS, happy in moderate light, and a real showpiece. Just get the gentle flow and coral spacing right.
What light and flow does a hammer coral need?
Low-to-moderate light (about 50–150 PAR) and gentle, indirect low-to-moderate flow. Too much flow keeps its tentacles retracted and can tear them.
Do I need to feed a hammer coral?
Not necessarily — it's largely photosynthetic. It's a subdued eater that benefits from an occasional meaty morsel like mysis, but doesn't demand target feeding.
Can I keep a hammer next to a torch or frogspawn?
Hammers, frogspawn and anchor corals are usually chemically compatible and can be placed near each other. Torch corals sting harder, so give a torch extra space even from other Euphyllia.
Sources & further reading
This guide was written and fact-checked against these authorities. It's honest, general guidance — not a diagnosis, and not a substitute for an aquatic vet or your own test kit:
- Tidal Gardens — Hammer Coral Care — light/PAR, flow, placement, feeding, sweeper aggression
- Saltwater Aquarium Blog — Hammer Coral Care — placement, feeding, Euphyllia compatibility
- Bulk Reef Supply — How to Care for LPS Corals — LPS chemistry (alk/Ca/Mg), feeding
Written and fact-checked by The Coralkin Team against marine-aquarist sources — if your hammer coral is struggling, it's almost always a light, flow or water-chemistry issue — check those first and ask an experienced reefer. We never guess a care number.
🔬 Review status: team-written and fact-checked against cited sources · not yet reviewed by a marine vet. How we research & fact-check →