Hammer Coral Care: Flow, Feeding, and Keeping Heads Happy

Hammer corals are the coral that makes visitors stop in front of your tank. Those fleshy, anchor-tipped tentacles swaying in the current look more like an anemone than a stony coral, and a thriving multi-head colony is one of the most satisfying sights in the LPS world. They are also — and this surprises people who lump all Euphyllia together — meaningfully hardier than their torch coral cousins, provided you respect three things: flow, chemistry stability, and their personal space.

Know your hammer: branching vs. wall

Two growth forms show up in shops, and the difference matters more than color:

• Branching hammers (Euphyllia ancora / paraancora, branching form): each head sits on its own skeletal stalk. They frag easily, isolate infections naturally (a dying head can be cut off), and are the form I recommend to almost everyone.
• Wall hammers: one continuous meandering skeleton. Gorgeous and often cheaper per square inch, but a tissue-recession event can travel the whole wall, and fragging is far riskier. Treat wall hammers as an intermediate-level purchase.

Australian-sourced hammers tend toward richer coloration and slightly touchier acclimation than Indo colonies. Whatever the source, buy heads that are inflated during store lights-on, with no exposed white skeleton at the tissue margin.

Water parameters: stability is the whole game

Hammers do not need pristine SPS water. They need unmoving numbers:

• Salinity: 1.025-1.026
• Temperature: 76-79F
• Alkalinity: 8-9.5 dKH — and steady. Alkalinity swings are the number one hammer killer in otherwise healthy tanks.
• Calcium: 400-450 ppm; magnesium 1300-1400 ppm
• Nitrate: 5-15 ppm; phosphate 0.03-0.1 ppm. Hammers in stripped-clean water shrivel and lose color.

Because hammers are stony corals, they consume alkalinity and calcium as they grow. In a small or heavily stocked tank that consumption outpaces water changes sooner than you expect. Test weekly with a proper alkalinity test kit and chart the numbers; a slow downward drift is your cue to start dosing before the coral tells you the hard way.

Flow: the make-or-break variable

Get flow wrong and nothing else matters. Hammers want moderate, indirect, randomized flow — enough that the tentacles sway continuously, never so much that they fold flat or bare skeleton shows between whipping tentacles.

Direct blasts from a pump cause tissue to retract and, over weeks, recede. Dead-calm water is just as bad: mucus and detritus accumulate between heads, and stagnant pockets invite brown jelly infections. A controllable wavemaker on a random or pulse mode, aimed across the tank rather than at the colony, produces exactly the chaotic-but-gentle movement Euphyllia evolved for. The visual target: tentacles waving like wheat in a breeze, extended fat and full.

Lighting

Moderate light suits hammers: roughly 75-150 PAR. Under a quality full-spectrum reef LED that usually means the middle or lower-middle of the rockwork, not the top. Too much light bleaches tissue and washes out the fluorescent tips; too little slowly starves the coral and dulls extension. As always, acclimate: start any new hammer low and shaded, then walk it toward its final PAR over two to three weeks. If your fixture has a percentage cap, dropping total intensity for a week after any new Euphyllia addition is cheap insurance.

Feeding

Hammers photosynthesize for the bulk of their energy, but heads visibly plump up on meaty feedings. Once or twice a week, with pumps briefly slowed, place a piece of mysis, chopped shrimp, or a coral pellet onto the tentacle crown of each head. Skip feeding if fish steal everything before the coral can swallow — a wide-mouth pipette and a little patience solve that. Overfeeding is rarely the coral's problem; it is a water quality problem, so scale feedings to your export capacity.

The sweeper tentacle problem

Hammers sting. At night, heads extend translucent sweeper tentacles several inches beyond the daytime silhouette and burn whatever they touch. Give a hammer colony a six-inch exclusion zone from anything that is not another Euphyllia. The commonly repeated exception is real but has limits: hammers, frogspawn, and octospawn generally tolerate each other and can be grown into a mixed Euphyllia garden — but keep torches out of it; torches hit harder and win. Placement fights are slow-motion disasters, and our guide to coral placement mistakes covers the spacing math for the whole tank.

Health problems and fixes

• Brown jelly disease: a gray-brown gelatinous film over a receding head, often after tissue damage. Act fast — siphon the jelly off outside the tank, frag off affected heads with clean bone cutters, dip the survivors, and improve flow.
• Tissue recession from the base: usually flow starvation, alkalinity swing, or pest irritation. Check parameters first.
• Bailout (a polyp detaching from its skeleton): an extreme stress response — chemistry shock is the usual culprit.
• Refusing to inflate: run the standard diagnostic — recent changes, flow, light, chemistry, pests, neighbors — before you touch anything.

A hammer that deflates at night is normal. A hammer that stays deflated through the photoperiod for more than a few days is asking for a parameter check.

Fragging branching hammers

This is genuinely easy on branching colonies: cut a stalk an inch below the head with bone cutters, glue the stub to a plug or rock, done. The colony responds by branching more. Never cut through live tissue on the head itself, and dip anything that leaves and re-enters the tank.

FAQ

Can hammer corals touch each other?

Different hammer colonies usually tolerate contact, and hammers generally coexist with frogspawn and octospawn. Keep torches physically separate — they are the most aggressive of the family and typically damage hammers in a fight.

Why is my hammer coral not opening?

Most often: a recent alkalinity or salinity swing, flow that is too direct, or a new light schedule. Test alkalinity first, then observe flow at tentacle level. Shipping and relocation sulk can also last a week — patience before intervention.

How fast do hammers grow?

A happy branching head typically splits into two over two to four months. A single frag becoming a ten-head colony in eighteen months is a realistic outcome in stable water with occasional feeding.

Hammers reward the boring virtues: steady alkalinity, moderate everything, and a respectful buffer zone. Nail those and the colony does the spectacular part on its own. For the full picture on stocking and growing out an LPS-centered reef, see our complete guide to coral care and propagation.