Hammer corals are one of the best-loved LPS corals in the hobby, and it’s easy to see why. Their thick, swaying tentacles with little anchor-shaped tips bring constant movement to a reef tank, and they come in everything from neon green to gold, purple and multi-coloured “splatter” forms. They aren’t the hardest coral to keep, but they do reward a stable tank and punish big swings. This guide covers everything you need to keep one thriving.
Quick care sheet
Scientific name | Fimbriaphyllia ancora (wall) / Fimbriaphyllia paraancora (branching), formerly Euphyllia |
Type | LPS (large polyp stony) |
Difficulty | Intermediate |
Lighting | Moderate (roughly 80–150 PAR) |
Flow | Low to moderate, indirect |
Placement | Lower to middle of the tank |
Temperament | Semi-aggressive – has sweeper tentacles |
Feeding | Optional, but helps growth |
Branching or wall hammer?
You’ll see two forms for sale:
- Branching hammer – each head sits on its own stalk. This is what most frags are, including all of ours. Branching hammers are generally the hardier of the two and much easier to frag.
- Wall hammer – one continuous, winding skeleton. Beautiful, but more sensitive and harder to cut.
You may also see hammers listed as Fimbriaphyllia rather than Euphyllia. Scientists moved hammers and frogspawn into their own genus in 2017. Torches stayed as Euphyllia. It’s the same coral – most shops still use the old name.
Water parameters
Stability matters more than hitting an exact number. These are what our own systems run at.
Parameter | Target |
|---|---|
Temperature | 24–25°C (75–77°F) |
Salinity | Steady at 1.026 SG (about 35 ppt) |
Alkalinity | About 8 dKH, within 0.2 either way |
Calcium | 400–440 ppm |
Magnesium | 1,300–1,400 ppm |
Nitrate | 5–15 ppm |
Phosphate | 0.05–0.08 ppm |
Hammers are sensitive to even small amounts of copper. Never add copper-based medication to a reef tank, and be careful with anything metal that touches the water.
Lighting
Hammers don’t need intense light. Moderate light – roughly 80–150 PAR – suits most. Too much light can bleach them, while too little turns them brown and slowly starves them.
Choose its permanent spot before it goes in, in moderate light with room around it, because hammers don’t like being moved. Our hammers are grown under moderate light, so a spot like that means little or no adjustment.
Flow
Getting flow right is the single biggest factor in a happy hammer. You want the tentacles to sway gently, not be pinned flat or blown inside out. Indirect, random flow is ideal. If your hammer stays half-closed, a pump pointing straight at it is the first thing to check.
Placement and spacing
The lower to middle part of the tank usually works best – on the sand bed or low on the rockwork.
Hammers have sweeper tentacles that can stretch several centimetres at night and sting neighbours. Give them at least 10–15 cm of space from other corals. They usually live happily next to other hammers and frogspawn, but keep an eye out even then. Leave room for growth too – a healthy branching hammer keeps adding heads.
What are sweeper tentacles?
Sweeper tentacles are the hammer’s defence system. They’re long, thin tentacles, much longer than the normal hammer-shaped ones, and often see-through, pale or whitish with a slightly sticky tip packed with stinging cells. The hammer sends them out to sting anything growing too close and clear space for itself.
You’ll mostly see them in the evening or after the lights go off, so it’s worth checking your tank with a torch at night. They can reach several centimetres past the coral and they grow longer if something keeps touching it.
Signs a neighbour is being stung: it stays closed, or a pale, bleached or receding patch appears on the side facing the hammer. If you see that, move one of them further apart.
Feeding
Hammers get most of their energy from light, through the algae living in their tissue. You don’t have to feed them, but small, occasional feeds will help them grow. Use a fine, meaty coral food or small frozen foods (like mysis or rotifers), gently puffed near the tentacles with a pipette once or twice a week. Feed little and often rather than a lot at once. In our own systems we feed all our corals Benepets coral food twice a week, and target feed meaty foods like mysis about once every two weeks.
When your new hammer arrives
- Float the bag or pot to bring it up to temperature.
- Acclimate slowly to your tank water.
- Dip it. We dip every new coral before it goes into our systems, using NYOS Coral Dip. Follow the label: it’s mixed in a separate container of tank water (never in the tank itself), at the standard dose of 10 ml per litre, with the coral left in for 10 minutes. Watch it while it’s in there and take it out if it starts producing lots of slime.
- Place it in its permanent spot, with moderate light, gentle flow and room around it.
- Don’t panic if it stays closed for a few days – hammers often sulk after travelling.
See our full acclimation and dipping guide for step-by-step instructions.
Common problems
Not opening. The most common causes are flow that’s too strong, a change in light, a swing in alkalinity or salinity, or simply settling in after a move. Check your parameters first, then the flow. Give it a few days before moving it again.
Turning brown. Usually not enough light, or too many nutrients. Raise the light gradually.
Bleaching (going pale or white). Too much light too quickly, or high temperature. Move it lower or reduce the light.
Brown jelly. A brown, jelly-like mass on the tissue, often with a strong smell of decay. It spreads quickly, so remove the coral from the display straight away. With a branching hammer you can often save the healthy heads by cutting off the affected one below the tissue and giving the rest an iodine dip (we use Seachem Reef Dip). Physical damage and big swings in water quality can bring it on.
Can you frag a hammer?
Branching hammers are some of the easiest LPS to frag. Cut through the skeleton between heads with bone cutters or a small saw, well below the fleshy tissue, and glue each piece to a plug. Wall hammers need a saw and carry more risk – only try it on a healthy, established colony. Afterwards, dip both the new frags and the parent colony in a good iodine dip to help prevent infection. We recommend Seachem Reef Dip.
FAQs
Are hammer corals good for beginners? They’re a good second step once your tank has been stable for a few months. Branching hammers are the more forgiving choice.
Can I keep a hammer next to a torch or frogspawn? Frogspawn, usually yes. Torches are more aggressive, so give a torch extra space and watch for any stinging.
Why does my hammer close at night? That’s normal. It may also put out its sweeper tentacles at night.
How fast do hammers grow? In a stable tank with steady alkalinity and the odd feed, a branching hammer will steadily add new heads.
Hammer corals from ReefGro
All our hammer frags are branching hammers, grown in our systems in Ipswich and shipped by Royal Mail Special Delivery. Because we grow them ourselves, stock comes and goes as each batch is ready. Have a look at our hammer collection, and if the one you want is out of stock, sign up for a back-in-stock alert on its page and we’ll let you know when it’s available again.
Every order is covered by our Live Arrival Guarantee – see our delivery page for details.