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The Hammer Coral Guide For Beginners and Experts

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This is in-depth guidance about a very beginner-friendly species  — hammer coral (a.k.a anchor coral). I explain every aspect of handling hammer coral: from water parameters to the best fragging technique. The article will be useful for beginners as well as for experts.

Basic Information

Scientific name: Euphyllia ancoraCommon name: Hammer CoralType of Coral: Hard (LPS)
Average size:up to 3 inchesOptimal Spacing: 5 inchesСomplexity: Easy

Whether you are just getting started with hammer coral or already keep one, you will find all the answers related to hammer coral. I made the article easy to skim, read subheadings to find answers as fast as possible.

Natural habitat and appearance

The Hammer coral is called that way because its tentacles form a T letter. It’s not rare for polyps to form the shape of a C letter, though. Hammer corals live within colonies in gentle waters near the seacoast. Mostly at depths around 90 to 130 feet. Сovering waters from the Indo-West Pacific (Fiji, Indonesia, Thailand) all the way up to the Solomon Islands. Hammer corals are also found near the Great Barrier Reef. 

They vary greatly in coloration, from pale shades of brown and somber gray to a dazzlingly bright palette! The most remarkable species have a fiery golden hue, while some corals take on a green or even neon coloring with bright tips. To protect that beautiful appearance, you should place them correctly within the tank.

Placement in a Reef Tank

As anchor corals inhabit tropical parts of the pacific ocean, they feel comfortable with relatively warm water and medium to strong water flow. Feel free to place anchor corals literally anywhere within the tank. They feel great both sitting on a sandbed in the corner and settling living rocks in the middle of the aquarium. 

Hammer corals are often hosted by clownfish. More info on how to get a clownfish to host a hammer coral can be found here. I have also compiled a list of corals and anemones suitable for clownfish, which you can find here.

The only rule here is to avoid extremes. Don’t expose the coral to excessive light, ultra-clean water, or aggressive neighbors. Provide around 5 inches of free space for safety purposes. Ideally, you want to keep all factors in balance. That can be achieved with careful observation. Once you’ve placed the coral, the next important matter is water quality. If the water is poor, the coral will never bloom to its full potential. The next paragraphs deal with water parameters.

Water Quality

Reef keeping success majorly depends (I would say more than half) on water parameters. High-quality water ensures your corals are bright and healthy. On the other hand, poor quality can cause a lot of problems to fix: from bacterias and algae to bleaching and death. The next paragraphs talk about key factors that form desirable high-quality water.


Provide hammer coral with 400 to 460 ppm calcium levels. Calcium is the major factor affecting the growth rate of any large polyp stony (LPS). I recommend starting with 400 ppm and growing 10 ppm weekly unless the coral feels great. Don’t forget that other corals in your tank may be sensitive to calcium. Always keep balance and adjust gradually. 


Hammer corals like alkalinity around 450 to 550 ppm, with 500ppm being the golden number. Alkalinity is crucial for marine species, so keep it as average as you can. This way, it’s easier to satisfy the needs of other tank inhabitants (without infringing on the rights of hammer coral)

Useful info: more than 75% of aquarists use 9 to 11 meq\L  Alkalinity (the equivalent of 450-550 ppm). Here is a conversion calculator.

pH (power of hydrogen)

You’ve probably heard me stress about keeping balance in a reef tank. Well, pH is the very essence of balance. Keeping pH level in the range of 8 to 8.3 is about perfect. 

You may have a reasonable question. What if the pH level is higher\lower? 

If pH in your aquarium is higher\lower, you WANT to adjust it to recommended values as soon as possible. Don’t rush when adjusting pH. The rule of thumb here is a step-by-step approach. To raise pH  —  add baking soda. To lower it, consider adding vinegar or lemon juice or “pH down” products (avoid ones with muriatic or sulfuric acids).

Useful tip: Schedule partial water changes (25%) monthly and plan smaller changes of 10-15% every week or fortnight to recover natural pH. 

Temperature and Flow

Hammer coral requires medium to turbid water flow and a temperature of about 76 to 84 degrees Fahrenheit. Remember Goldilocks and the three bears? Medium water and flow are not too much or too little but just about perfect. If you overdo the flow, it can prevent the growth or even rip the polyps off. The same with temperature balance, too hot water causes bleaching and bacterial emergence.


Stick to the medium indirect PAR. Hammer corals are tolerant to bright lightning only if the light is diffused (non-direct). That is why you don’t want to use metal halides. The normal value to start with would be 120-170 PAR. Going out of that range is a personal risk that you are not willing to take.

As for spectrum, I suggest 400-470nm. Tend more to the blue part of the spectrum instead of white. A great ratio to combine both would be 60\40 with the dominance of the blue spectrum. I expose corals for 10 hours with 60% blue and 6 hours with 40% white.

But avoid too much white spectrum(not more than 40%). I make 60% blue for 10 hours and 40% white for 6 hours. For another 8 hours, I put the lights on hold. LEDs are the best for hammer corals, followed by T5, and metal halides (not recommended, but it also works if adjusted properly)

Compatibility with Other Species

Here are some popular animal species to keep hammer coral with:

EasyMay Cause Problems
GroupersDwarf Angels

When it comes to compatibility with other corals, it’s convenient to split them into 3 categories. Aggressors, defensive and passive. Here is the relationship among types:

AggressiveNot compatibleNot compatibleMaybe
DefensiveNot compatibleCompatibleCompatible

Hammer corals are aggressive. They have stinging tentacles that can harm other corals or even small fish. As a rule, corals that live in the same environment do not attack each other. For example, if both corals were found in the waters of a large barrier reef where they lived in close proximity, you will have them peacefully coexist in the aquarium.

Also, if the corals belong to the same family, they will not attack each other. In the case of hammer coral, this applies to corals in the Euphyllia family (branching coral, frogspawn coral, torch coral, grape coral, etc.) If you already have other corals, make sure you leave enough room so the hammer coral can not reach out with its tentacles to the neighbor. Usually, 5-6 inches is enough.

The Biggest Problems Related to Hammer Coral 

Let’s talk about how to solve those problems.

Not opening 

Hammer coral may have problems with opening up when first transferred to a new tank. If your newly purchased (or fragged) coral is not opening for 1 to 3 days, that is normal. Give it some time to adjust. Once 3 days are gone, and your hammer coral is still retracted or shrunk, experiment with placing. For example,  If the coral lived on the sandbed, replace it to the corner, sit on the living rock, etc. Most of the time, replacing solves the problem. If your hammer coral is still not opening up, adjust water parameters.


Coral can lose its color due to stress. Unbalanced pH, temperature, water flow, contamination can cause major stress. If you’ve noticed that your hammer coral is not as bright as it once was, make a partial water change, then clean the water. 

The best way to treat\prevent bleaching is to keep the coral environment in balance. Provide good alkalinity, water flow, lightning to stop bleaching. I recommend partial water changes (10% to 15%) weekly or any other week.


Hammer corals are inherently aggressive. Make sure to provide at least 5 inches of space to protect more peaceful corals (or other aggressive species). In some cases, a hungry coral can extend its tentacles up to 10 inches in search of food. That is why adequate lighting is an absolute must. Keep your PAR around 120 to 170. If you can not provide more light (because other corals are sensitive, for example), consider targeted feeding. Feeding hammer coral may reduce aggression toward other species.


Brown jelly disease, bugs, flatworms are just a little part of infections that can harm your coral. To prevent infections, always clean the filtration system and dip new corals before introducing them into the aquarium.

Examine the hammer coral carefully for parasites and then immerse it in the solution. In the best-case scenario, the parasites will die immediately. Sometimes you will have to remove stunned parasites by hand.

Feeding Hammer Coral

You don’t have to feed hammer corals. They obtain energy from symbiont alga which lives inside the coral. Provide coral with enough light instead of feeding. 

Although hammer coral can consume fleshy, meaty food, I don’t recommend feeding. For small aquariums, excessive food causes contamination. Even if you clean up the aquarium often enough (to prevent the spread of bacteria, algae, and other microorganisms), feeding may not be worth the effort. Many aquarists note that additional feeding didn’t impact the growth or appearance of the coral majorly. 

Tip: Feeding the hammer coral may reduce its level of aggression towards neighboring corals.

To feed the hammer coral, use meaty food, such as fish products, copepods, krill, brine shrimps, etc. You can feed directly using a turkey baster as well as a transfer pipette or thin the food out in a separate container. It will reduce the consumption time for the coral (food is digested faster = less contamination). Also, don’t forget to turn off the water circulation system (as it spreads the food particles all over the aquarium). 

Don’t forget to install a protein skimmer and filtration system to eliminate the effects of contamination from feeding the corals with food containing protein and amino acids.

Conclusion: I don’t suggest targeted feeding of hammer coral. Instead, you may want to focus on key parameters such as water flow, lighting, etc. My opinion is backed up by the following scholarly work.

How To Frag Hammer Coral

Hammer corals have sweeper tentacles that may sting. Make sure to take safety precautions seriously as toxins are no laughing matter. Use goggles and gloves to protect your eyes and skin from toxins.

To frag hammer coral, I use a Dremel. However, other methods also work. The major benefit to using a Dremel is that you can get an immaculate straight cut (making it easier to glue the cutting onto a frag plug or frag disc later).

There are 3 types of hammer corals: wall, branching, and mix of both. Wall hammer corals require a more careful approach as the growth rate is much slower than branching or mixed type. What makes wall varieties tricky to propagate is that there’s rarely a convenient place to make an easy cut. The first thing you want to do is to spot the darkest area possible. Start fragging from the darkest spot as it’s the oldest.  The rest of the fragging is the same for all types. 

Branching varieties look like a tree. Buds form at the base of the polyp and grow into new heads over time. The normal time frame is 12 to 18 months. During that period, a single polyp can multiply drastically to form a large colony.

Despite the type, you should use Iodine disinfectant to help the healing process once you’ve made the cut. It’s easy to use: dissolve disinfectant in the water and spread over the damaged area. I only recommend Iodine if you damaged the coral significantly. (don’t use disinfectant for healthy, untouched coral as it may cause stress)

When the cut is healed, you are ready to superglue the frag to a disc. This way, it will be easier to organize and put the frags into the tank. Usually, glue takes a few minutes to set up. Once that happens, you can put the frag into the tank (the glue can cure under the water). If you are one of those who doesn’t like the “artificial” glue method, consider the rubber band or any other way to set up the frag. As long as your frag is standing upright under the water, any method is perfect.

Hammer corals are definitely not of those capricious corals which require tons of attention, subtle parameters, and specific conditions. Where you drop it, that’s where they start to grow. If you provide just a little bit of attention, hammer corals will splash their beauty all over the aquarium.

As you see, hammer coral requires a little touch of attention. It’s not aggressive and adapts to almost any adequate conditions. hammer will not cause any problems, which makes it a perfect fit for beginners (of course if you provide adequate water quality, minerals)