Are you looking for a great LPS (large polyp stony) coral that will take center stage inside your aquarium without being too challenging? If so, the hammer coral makes a great choice!
The hammer coral (Euphyllia ancora) is a popular LPS coral that is a must-have for reef tanks. They are bold corals that come in various colors and growth morphs, with beautiful large fleshy polyps that wave around in the water flow, creating the ultimate coral reef display in your home.
What Are Hammer Corals?
The hammer coral is a staple LPS coral found in most reef tanks in the world. This mesmerizing coral is also often referred to as the anchor coral because of its anchor-shaped tentacles, adding to its unique look.
During the night, the hammer coral will hide in its skeletal base, but do not worry, because, during the day, its polyps are on full display to show off to anyone walking by your aquarium.
The hammer coral is known for its dramatic coloration, coming in green, tan, or brown with lime green or yellow tentacle tips that magnificently glow under actinic lighting. Some hammer corals are branched, which often confuses beginner reefers due to their similar appearance to torch corals.
Beginner hobbyists may also find them slightly challenging because they are fairly difficult to maintain, but taking on challenges will only improve your coral husbandry efforts! As long as you are maintaining proper water conditions, your hammer coral will thrive.
Hammer Coral Summary
- Scientific/Latin Name: Euphyllia ancora
- Family: Euphylliidae
- Common Names: Hammer Coral, Anchor Coral
- Care Level: Moderate
- Temperament: Aggressive
- Lighting: Moderate (PAR 80-150)
- Water Flow: Moderate
- Placement: Low to middle
- Growth: Slow to moderate
Where Do Hammer Corals Originate?
Hammer corals originate from the western regions of the Indo-Pacific. If you have been scuba diving in and around Fiji, the Great Barrier Reef in Australia, the Solomon Islands, or Tonga, it is very likely these epic corals were on the shallow reefs.
Their distribution on the reef exposes them to moderate currents, allowing their polyps to gently flow, with the water movement.
The hammer coral tends to stay in shallow waters, rarely exceeding 130 feet (40 m). Unfortunately, due to the demand of the aquarium trade, the natural range of hammer corals has been overharvested, and now they are listed as vulnerable, according to the IUCN Red List.
The good news is that hammer corals can easily be fragged, so wild collection is no longer in demand.
What Do Hammer Corals Look Like?
Hammer corals get their name from their hammer or anchor-like-shaped polyps. When extended, hammer corals take on three different polyp forms:
- T-shaped: These polyps have a flattened tip, which looks like an everyday hammer you would have at home.
- Curved: Some hammers have a curved end that pulls back towards the tentacle base, resembling an anchor.
- Round: Round hammers have a more ‘bubbly’ shape, with round inflated polyps, like mini balloons. This morph often confuses many reefers, particularly beginners, because they look similar to frogspawn or torch corals. However, if you look closely, hammer corals have much shorter tentacles compared to torch corals and frogspawns are more spherical.
Like other Euphyllia corals, hammer corals also come in branching and wall types.
Branching hammer corals look like broccoli with a single cluster of concentrated polyps, while wall-type hammer corals have an extended base, sometimes growing in a “U” or “V” shape. Branching hammers are the most common in aquariums because they grow fast and are generally easier to care for, but don’t let that put you off wall hammer types, as these are also fantastic corals!
In terms of color, the hammer coral does not disappoint… You have a choice of many colors including green, blue, orange, pink, and purple, that are often fluorescent under the right lighting conditions.
Most hammer corals you come across will have dark tentacles with lighter ends, however, some hammer corals have only one color. Some have more unique color morphs, such as the Aussie Rainbow Micro hammer, which are often difficult to track down.
Hammer Coral Care
Hammer corals are fairly challenging to care for, as they require stable water parameters, moderate lighting, moderate water flow, and supplemental feeding.
Tank Parameters For Hammer Corals
A crucial part of coral husbandry is maintaining stable water parameters, and this is no different when caring for hammer corals.
- Temperature: 72° – 78 °F
- pH: 8.1 – 8.3
- Salinity: 1.024 – 1.026 (1.025 preferred)
- Alkalinity: 8 – 12 dKH
- Nitrates: <10 ppm
- Phosphates: <0.10 ppm
- Calcium: 350 – 450 ppm
- Magnesium: 1200 – 1350
It is extremely important to maintain consistent levels of calcium, alkalinity, and magnesium levels when caring for hammer corals. As your hammer coral is a type of LPS coral, it requires these three compounds to grow its calcium carbonate skeleton.
Depending on which hammer coral you have, and its growth rate and size, will determine the amount of calcium, alkalinity, and magnesium supplementation you’ll need. The faster your hammer coral grows and the bigger it gets, the greater amount of these compounds are required.
Calcium and alkalinity are the most important, and without sufficient levels, your hammer coral may start dying. Therefore, it is best to aim for calcium levels between 350 and 450 ppm, but 400 ppm is perfect.
Hammer Coral Reproduction
In the wild, corals take part in mass spawning events where they release eggs and sperm into the water at the same time, in the hope they meet to form gametes (offspring). This can happen inside your aquarium, however, it is highly unlikely. But, that is not to say that natural spawning will never happen in your reef tank, plus, this is the biggest achievement in coral husbandry for many reefers.
Part of coral husbandry is learning to lend your hammer coral a helping hand with reproduction by propagating it. Propagating corals in aquariums is known as fragging. This is where you manually split the hammer coral.
How To Frag (Propagate) Hammer Coral?
Depending on which variety of hammer coral you have, fragging is pretty easy.
If you have a branching hammer coral variety, fragging these types require much less work, and they generally are more successful. This doesn’t necessarily mean you can’t frag wall varieties, but it does require much more patience.
Fragging Branching Hammers
- First, look for a healthy part of the coral colony.
- Next, snap off one of the branches, or if that is too difficult, you can cut off a section with pliers or a knife from a propagation kit.
- Dip both the mother colony and the coral frag in an iodine solution to reduce the chances of infection.
- Finally, glue the hammer coral frag to a frag plug or piece of rock with reef-safe IC gel glue or putty.
- Once the coral frag is secure, place it at the bottom of the tank to give it time to heal, before you put it in its final placement.
Fragging Wall Hammers
- Most of the steps are the same as fragging branching hammer corals, but the tool you use will be different.
- To frag a wall hammer, you will need to use a Dremel tool.
- You will need to wait for the wall hammer to retract its polyps, so you can see where you are cutting through. You need to aim the Dremel directly through the base.
- Just like branching hammer corals, you also need to dip the wall hammer in iodine after fragging.
- Gluing a wall hammer to a frag plug or piece of rock is the same as fragging branching hammers, but you can reshape the base to the shape you wish.
- Once the coral frag is secure, place it at the bottom of the tank, the same as for branching types.
Hammer Coral Growth
Hammer corals are slow growers at the beginning because of the calcium carbonate skeleton they must build. Saying that, once they have fully settled into their new home, they can grow fairly quickly, if their captivity requirements are met.
Some hammer corals will have good growth within the first few months, while some may take a few years to fully establish.
To promote faster growth, pay close attention to the lighting and PAR levels, and your feeding routine.
Hammer Coral Lighting & PAR Levels
Your hammer coral only needs moderate lighting for the zooxanthellae to perform photosynthesis. For a moderate amount of light, a PAR between 80 and 150 is suggested. To maintain the PAR levels inside your aquarium, it is recommended to invest in a PAR meter, however, if you are not there yet, then you can ask your local fish store (LFS) to rent one.
Some hammer corals will extend under subdued lighting, while others will show off their colors under stronger lighting. So, always check the lighting requirements for your particular type of hammer coral with your LFS.
You’ll want to hit your hammer coral’s sweet spot, otherwise, you will run into issues…
A prime example of too much lighting is coral bleaching. This is where your hammer coral expels the symbiotic algae (zooxanthellae) that live inside its tissues, leaving it looking ghostly white. Too much lighting can also cause your hammer coral to curl its polyps inwards toward the base.
On the other hand, if your lighting is too low, your hammer coral will lose its beautiful coloration, start starving and become stressed, putting it in danger of infections and diseases.
What Type Of Lighting Do Hammer Corals Need?
As hammer corals thrive under subdued lighting, metal halides are not recommended. The best lighting fixture for your hammer coral are LED lights, followed by T5s, and as a last resort metal halides. Metal halides can be used, BUT, they must be adjusted properly to meet the PAR and spectrum levels.
A spectrum of 400-470 nm focused more on blue light (60%) than white light (40%) is a great choice. You don’t want to expose your hammer coral to white light, for longer than 6 hours per day.
Hammer Coral Water Flow Requirements
Moderate flow is key for hammer corals, not too much or too little, but something in the middle, to hit their sweet spot – think of Goldilocks!
You also want to direct the powerheads away, so your hammer coral is not being blasted. If you blast your hammer coral it will put too much pressure on the polyps causing them to bend over the skeleton and risk tearing the tissues.
Another issue with too much water flow is polyp retraction; hammer corals are known to close up when the water flow is too strong, in an attempt to protect their polyps.
But, on the other hand, if the water flow is not strong enough, algae and detritus can easily build up on the hammer’s polyps.
Do Hammer Corals Need Feeding?
Most corals get the majority of their nutritional requirements from the zooxanthellae inside their tissues, and while hammer corals may not be the most active or ravenous eaters, they do benefit from the occasional feeding of something meaty!
Types of food that hammer corals love, include:
- Enriched brine shrimp
- Mysis shrimp
Feeding your hammer coral is fairly simple, and you only need to feed them a couple of times a week to keep them happy and healthy. To feed your hammer coral, take a turkey baster and gently release the food directly above your corals. Whatever your coral doesn’t eat, any fish you have will usually devour the leftovers.
Hammer Coral Placement
Hammer corals are flexible when it comes to placement in aquariums, as long as the water flow and lighting requirements are met; take a look at your lighting and water flow, and place them accordingly. However, they generally do best when placed at the bottom of the tank in the sand, or in the middle region on rocks.
One thing you must consider is their neighbors, as, like other Euphyllia corals, the hammer is known for its aggressive nature, stinging corals that get too close with their long tentacles.
Can Two Hammer Corals Be Placed Next To Each Other?
Hammer corals are peaceful towards other hammers, so you should have no issues when placing them next to each other. Hammer corals can also be placed close to other Euphyllia corals such as frogspawns, torch corals, and grape corals.
Because of this, most keen LPS collectors will keep many Euphyllia corals in the same reef tank, and who blames them, Euphyllia corals create an epic display!
Hammer Coral Aggression & Compatibility
As mentioned, hammer corals are considered to be aggressive, so your hammer WILL take a strike at anything that gets too close.
The aggressiveness comes from specialized stinging cells called nematocysts, found at the end of your hammer’s sweeper tentacles. The nematocysts will sting and chemically burn any neighboring corals, including other LPS corals, if they don’t swipe first!
So, to prevent chemical warfare, always give your hammer coral plenty of room inside the aquarium. You want your hammer to grow out into the beautiful coral it is, but also allow enough space to keep them out of trouble.
Still on the topic of aggression, comes compatibility with fish and invertebrates. Now, I’m sure you want to add some awesome fish and maybe some critters to finish off your mini-ocean look. Some fish or invertebrates even have a symbiotic relationship with corals, however, not all marine creatures will become best friends with LPS corals like your hammer.
The biggest “no-no” when we talk about compatibility is adding fishes or invertebrates that are known for nipping corals. These include most butterflyfish, angelfish, and rabbitfish.
But, do not worry, as there are still some incredible tank mates you can add to your aquarium!
Suitable Tank Mates For Hammer Corals
If you are looking for some tank mates to give your reef tank an even more tranquil space in your home, then I recommend the following:
Even though the above are all considered “reef-safe”, always keep an eye on how your hammer coral is responding to their new inhabitants. If your hammer coral is becoming distressed, consider removing its irritating friend!
Tank Mates To Avoid!
So, now you know which tank inhabitants are considered reef-safe, but, it is also important to know which tank mates should be on red alert!
When keeping hammer corals, you should avoid:
- Emerald crabs
- Hermit crabs
- Peppermint shrimp
Now, you may be wondering why the peppermint shrimp is on this list…
Well, despite many LFS selling these funky-looking shrimp because of their willingness to eat aiptasia anemones, which causes many issues for hammer corals and other corals with luscious fleshy polyps, the peppermint shrimp is known to cause utter chaos for hammers. Peppermint shrimps are usually going to cause more damage than good for your hammer coral, so it is best to avoid these types of shrimp!
The great news is, that hammer corals are safe to keep with any other shrimp that is known to be reef-safe.
Can You Touch Hammer Corals?
Even though your hammer coral contains stinging cells, you can touch them without being hurt. So, if you need to gently handle your hammer coral to move it inside the aquarium, or to remove it for fragging, then you will be fine. Saying that, if you are very, very sensitive to irritants, then you may feel a slight tingle, but that’s it.
Just because you can touch hammer corals, it does not mean you should be petting them daily like our furry four-legged companions. Corals cover themselves in a protective layer of mucus, and when you touch your hammer coral, some of this mucus will come off, which can expose it to bacterial infections and other diseases.
If you need to handle your hammer coral, the best place to touch is its stony skeleton underneath its polyps. This avoids tearing or damaging its delicate, long fleshy polyps.
Hammer Coral Pests, Diseases & Common Issues
As your hammer coral has an aggressive nature, it puts your hammer in a better position than most corals when it comes to surviving pests and diseases. However, even though your hammer can survive in less pristine water conditions, there are some health issues you need to be aware of.
Acoel Worms & Euphyllia Eating Flatworms
Let’s dive into the most irritating of them all… acoel worms and Euphyllia eating flatworms.
Both these worms absolutely adore hammer corals. If these guys get into your aquarium and onto your hammer coral, they will soon make your hammer’s coral base a home, devouring your coral in the process. After some time, you will find yourself with an infestation, eaten hammer coral, and higher waste pollutants in the aquarium water.
Luckily, the worms and egg masses are big enough to see with your eyes, making them relatively easy to eradicate. To remove them, dip your hammer coral in a coral dip, or you can add some wrasses into the aquarium. Wrasses are not only beautiful, but they are also a perfect solution for pest control!
Brown Jelly Disease
Next on the list is the dreaded brown jelly disease. The actual cause of brown jelly disease outbreaks in hammer corals is still not known, but the infection seems to happen after the hammer coral becomes injured.
Once your hammer coral is infected with brown jelly disease, a brown substance that looks like jelly (hence the name!) will cover the surface of your coral. This is a serious condition that can easily kill your hammer coral if ignored and left untreated.
The brown jelly disease also affects other Euphyllia corals, easily spreading from one to the next.
Unfortunately, the brown jelly disease is difficult to treat, and many hammer corals will not recover from the outbreak. However, that is not to say that all hope is lost. There are a few things you can do to try and treat the infection.
Increasing the water flow inside your aquarium is the first step. Increasing the water flow increases the amount of oxygen and nutrients that your hammer coral receives, which benefits the overall health of your coral. But, increasing the water flow only works if the brown jelly infection is localized.
If the water flow is not improving your hammer coral’s condition, then you can try fragging it. Many hobbyists are hesitant to frag infected corals, but if the brown jelly disease is severe, then it’s necessary for your hammer coral’s survival.
When fragging your hammer, suck up any brown jelly from its tissue with a turkey baster before fragging it. You should also turn off any powerheads to prevent the brown jelly from moving onto other corals inside your aquarium.
Part of the fragging process includes an iodine dip, and this is also a suggested method to remove the brown jelly disease. Iodine is great at treating different coral-based illnesses. Soaking your hammer coral for 10-30 minutes in Lugol’s iodine may save your coral.
Aiptasia Sea Anemones
Aiptasia anemones are a common and unwanted guest in reef tanks. These opportunistic anemones are capable of multiplying rapidly and aggressively competing for space and food. They are hitchhiker masters, found backpacking on reef rocks and coral colonies, waiting for the perfect time to plague your aquarium.
Once infected, your hammer coral will produce excessive amounts of mucus, expelling the zooxanthellae, and changing its color. So, if you notice any of these signs and symptoms, you need to act fast, as once your hammer expels all the symbiotic algae, it will be too late to save your hammer coral.
As aiptasia are resistant to your hammer coral’s stinging sweeper tentacles, they will soon swarm your coral if they are hiding somewhere between your coral’s polyps. Another headache we hobbyists face is their resistance to ‘ordinary’ coral dips.
But, do not panic, as many hobbyists HAVE been successful in killing off aiptasia sea anemones!
It requires a syringe (and needle) to inject the aiptasia with a chemical/liquid solution:
- Lemon juice concentrate: Inject 0.5 ml of lemon juice into the base of the anemone.
- Sodium hydroxide: Remove the anemone from the aquarium, and pour the solution over the entire aiptasia. This has a 100% mortality rate.
- Calcium hydroxide: Inject the aiptasia with the solution. Just be sure to remove the anemone beforehand, so the calcium doesn’t affect the pH of your aquarium water.
- Hydrogen peroxide: Probably the quickest way to kill aiptasia anemones. Inject the hydrogen peroxide into the anemone’s base and it will melt.
If you don’t want to use a chemical or liquid method, then you can try adding natural predators, such as butterflyfish, filefish, puffers, shrimp, and hermit crabs.
However, it is important to check that they are considered reef-safe, so you do not add any more problems for your hammer coral.
Where To Buy Hammer Corals?
Hammer corals are a staple in reef aquariums, which means they are available at most LFS, and if not, you will certainly find them online.
When buying hammer corals, you want to look for big and fat colonies with fully extended polyps and bright coloration. Stay away from any discolored or white-looking hammers with retracted polyps, as these are signs of an unhealthy coral.
Hammer corals are top of the list when it comes to LPS corals for reef aquariums. They are perfect candidates for anyone that has successfully kept soft corals and easy LPS corals like the candy cane coral or acan brain coral. If you haven’t, before buying a hammer coral from your LFS or online, try some bulletproof soft corals and see how you get on, as hammers are notoriously more challenging!
After mastering softies, hammer corals are perfect stepping stones to the land of stony corals. Just remember to keep their tank conditions stable and allow plenty of space for them to grow and thrive without stinging neighboring corals with their long sweeper tentacles.
Once you have met your hammer coral’s care requirements listed in this article, you will be rewarded with a moderately easy coral to care for, and of course, a mesmerizing addition to your reef tank that should hopefully thrive for many years!