An easy-to-understand, comprehensive guide to Hammer Coral care based on over 30 years of reefkeeping experience.
Hammer Coral Care at a Glance
These values reflect our husbandry practices and are intended as guidelines, not rigid requirements. Hammer Corals can thrive across a range of stable conditions. Consistency matters more than chasing exact numbers.
Hammer Coral Lighting Requirements
Most Hammer Corals in our systems are healthy and grow under 50–150 PAR. We occasionally keep specimens at approximately 200 PAR, but some varieties bleach at that intensity.
For stronger lighting, our approach is gradual acclimation. Start in a lower-PAR location and move the coral toward higher light over approximately one to two months, watching for changes in polyp extension and coloration. Some lightening of the coral's color can be normal as it adjusts to increased illumination, but excessive or rapid lightening can be an early warning sign of bleaching. If the coral becomes noticeably pale, reduce light exposure rather than continuing to increase PAR.
Does higher PAR produce brighter colors?
Hammer Coral coloration can change substantially with lighting and water conditions. Some varieties in our care develop more colorful stems only after receiving approximately 100 PAR or more. That is an observation about particular strains, not a reason to expose every Hammer Coral to stronger lighting.
We've observed different stem coloration on polyps from the same Holy Grail Hammer colony. A polyp in lower light showed predominantly darker stems, while a polyp receiving more light developed noticeably greener stems. These photographs illustrate the difference without suggesting that PAR was the only possible factor.
These photographs document differences in coloration within the same Holy Grail Hammer colony. Although several factors can affect coloration, lighting can play an important role. Most Hammer Coral varieties don't exhibit such dramatic changes. Avoid exposing a coral to excessive light simply to achieve a modest improvement in coloration.
Water Flow: Why Hammer Coral Varieties Differ
Moderate flow works for most Hammer Corals. In our systems, polyps often extend more fully at the lower end of that range. Water movement should gently move the tentacles rather than forcefully compress them against the skeleton.
Reduced extension can indicate excessive flow, but it can also result from excessive light or unstable water chemistry. Consider the complete environment before assuming flow is the problem.
An important low-flow exception
Some Australian Hammer Corals, including the variety known as Pure Toxic, have distinctive rounded tentacle tips and prominent skeletal ridges.
In our experience, these varieties can be injured even by flow that would be considered moderate for most Hammers. Under too much movement, their polyps may remain closed and their delicate tissue can be damaged.
Our practice: Maintain these specimens in low flow. After several days of acclimation, healthy polyps should extend well beyond their prominent skeletal ridges. Failure to extend may indicate that the coral is experiencing excessive flow or another source of stress.
Placement, Spacing & Coral Compatibility
We generally place Hammer Corals securely on aquarium rockwork. In high-light, high-flow mixed reefs—especially tanks also housing Acropora—we usually recommend the bottom half of the aquarium.
In aquariums dominated by LPS and soft corals, Hammer Corals can be placed at various heights, provided their individual light and flow requirements are met.
Secure attachment is essential. A dislodged Hammer Coral can injure itself and sting corals below it. Leave room for tentacle expansion and future growth rather than arranging frags solely around their present size.
Can Hammer and Frogspawn Corals Touch?
Hammer and Frogspawn Corals can almost always touch without harming each other. We've maintained mixed gardens using these corals, combining different colors and tentacle shapes in the same display.
Individual colonies occasionally behave differently, however, so monitor contact points for corals retracting away from their neighbor. Avoid forcing colonies tightly together, particularly while newly introduced.
Do not assume Torch Corals are equally compatible. Torches can be more aggressive toward neighboring Hammers and Frogspawn and should be given additional separation.
Water Chemistry: Consistency Comes First
At Lucky Corals, we keep our Hammer Coral systems at approximately 76–78°F with alkalinity near 8.0 dKH. Salinity, calcium, and magnesium are maintained close to natural seawater levels.
We choose these conditions partly because they are close to the values used by many of the wholesalers and importers from whom we receive corals. Matching familiar conditions helps us minimize unnecessary stress due to environmental changes when new specimens arrive.
For customers, we generally recommend selecting a salt mix that produces water chemistry close to natural seawater and then maintaining those values consistently.
A slightly less-than-ideal but stable value is often preferable to an ideal value that fluctuates repeatedly. Choose reasonable targets, measure consistently, and avoid making abrupt corrections solely to achieve a particular number. This is especially relevant to pH, which reefkeepers sometimes attempt to adjust repeatedly, creating more instability than the adjustments resolve.
Do Hammer Corals Need Direct Feeding?
We normally do not directly feed most Hammer Corals. They capture small amounts of food missed by fish and can benefit from the nutrient availability of an established aquarium with fish present.
In our experience, Hammers generally perform better in established systems with fish than in systems with very limited nutrient input. This is not a recommendation to overfeed an aquarium or to allow nutrients to become uncontrolled.
When we do target feed
We often make an exception for the low-flow Australian Hammer types discussed earlier. They exhibit a strong feeding response and may be especially vulnerable to injuries resulting from improper shipping.
We've observed that appropriate feeding can support recovery in some injured specimens and may influence whether a compromised coral recovers or continues to decline.
Branching vs. Wall Hammer Corals
Branching and wall Hammer Corals can both thrive in stable aquariums. Their different skeletal forms do, however, affect how localized damage can progress.
Branching Hammers
Branching Hammers develop physically separated heads. When one head is injured or affected by disease, the damage may remain localized while other heads continue growing.
That separation offers an advantage when a colony suffers localized tissue loss.
Wall Hammers
Wall Hammers have a continuous skeleton and connected tissue. Injury or disease affecting one portion can sometimes progress across the entire specimen.
Nevertheless, a healthy, fully healed wall frag—or an unfragged wall specimen—can be hardy in stable conditions.
We believe some of the historical reputation of wall Hammers as difficult corals was influenced by commercial practices: wall specimens were often fragged and sold without enough time to heal.
This doesn't eliminate the practical benefit of separate heads on branching colonies, but it is an important distinction when evaluating healthy wall Hammers.
Acclimating a New Hammer Coral
Our usual temperature-acclimation practice is to float a sealed shipping bag for approximately 15 minutes, extending to around 30 minutes if the shipment arrives particularly cold.
Once temperature has been equalized, minimize unnecessary handling and follow a suitable dipping and pest inspection procedure.
We recommend avoiding strong illumination for the first couple of weeks, particularly if the new specimen is not in optimal condition.
If the long-term location will receive relatively high PAR, acclimate the coral gradually over approximately one to two months rather than placing it directly under intense light.
Common Problems & Pest Prevention
Reduced polyp extension
Contracted polyps can indicate excessive flow, excessive illumination, or unstable water conditions. Look for recent changes and evaluate the specimen rather than making several adjustments simultaneously.
Physical injury
When handling Hammer Corals, avoid crushing or scraping flesh against the skeleton, particularly near the stalk and tissue boundary. Mount specimens firmly so they cannot fall onto neighboring corals.
Euphyllia-eating flatworms
Euphyllia-eating flatworms are frequently associated with Torch Corals but can also infest Hammer Corals. Inspect incoming specimens carefully, especially the tissue-skeleton boundary beneath the polyp where flatworm eggs are deposited.
We recommend an appropriate coral dip, used according to the product's directions, to help dislodge visible pests. Dips containing Melaleuca (tea tree) oil smell nice and are effective at dislodging flatworms. Gently swirling the coral in the dip helps detach flatworms. Dips do not eliminate eggs. Egg deposits must be located and carefully removed, and quarantine with follow-up inspection is strongly preferable where possible.
If a suspected infestation cannot be managed safely, returning the specimen or declining to introduce it may be a better choice than exposing an established coral collection.
How to Choose a Healthy Hammer Coral
For a reefkeeper trying Hammers for the first time, we recommend beginning with an inexpensive specimen. If it thrives in your aquarium, you can become more selective with subsequent additions.
Reef tanks fill up quickly. Taking time to select genuinely desirable varieties can lead to a more satisfying collection than buying many corals simply because they're available.
We also suggest approaching unfamiliar vendors cautiously. Inspect corals carefully for pests and signs of poor health, and research customer experiences before buying.
Look at negative reviews as well as positive ones. How a vendor responds when an order has problems can reveal a great deal about its standards. Be cautious of coral vendors using photographic filters, excessive saturation, or camera settings that exaggerate coloration. These techniques can make corals appear substantially more colorful than they do in person.
- Prioritize stability over constantly chasing exact parameter values.
- Learn from an affordable specimen before purchasing expensive varieties.
- Choose healthy, pest-free corals from vendors whose practices and customer support you trust.
Hammer Coral Care FAQs
What PAR is best for Hammer Corals?
Most of our specimens do well between 50 and 200 PAR. Some tolerate approximately 250 PAR, but others can bleach at that intensity.
Do Hammer Corals prefer low or moderate flow?
Moderate flow works for most, often with fuller extension at its lower end. Certain Australian varieties with prominent skeletal ridges need low flow.
Can Hammer and Frogspawn Corals touch?
They usually can, and we maintain mixed gardens. Compatibility isn't guaranteed for every specimen, so observe contact points and allow space for growth.
Do Hammer Corals need direct feeding?
We don't routinely target feed most Hammers. We do sometimes feed certain Australian strains and recovering specimens that show a strong feeding response.
Why isn't my Hammer Coral opening?
Excessive flow, lighting, unstable parameters, recent shipping stress, injury, or pests may be involved. Check the coral and its environment before making changes.
Are branching Hammers easier than wall Hammers?
Branching specimens have a structural advantage because an injured head may not jeopardize the entire colony. Well-healed wall Hammers can nevertheless be hardy.
About the Author — Eric Arnell
Eric Arnell founded Lucky Corals in 2018 and has been keeping reef aquariums since 1995. His experience includes coral husbandry, aquaculture, sourcing and evaluating coral strains, and working with a wide variety of LPS corals. The care recommendations in this guide draw on his firsthand reefkeeping experience and observations from Lucky Corals' coral systems.