Acan, Torch, and Hammer Coral Care Guide
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The reef aquarium hobby is often defined by the vibrant colors and hypnotic movements of Large Polyp Stony (LPS) corals. Among the most sought after species are the Acan, the Torch, and the Hammer coral. These three corals represent some of the most stunning biological diversity found in the ocean, offering a mix of fleshy textures, flowing tentacles, and architectural skeletal structures. While they are often grouped together in the LPS category, each has its own set of specific requirements and personality traits that a successful reef keeper must understand. Whether you are captivated by the rainbow patterns of a Micromussa or the swaying gold tentacles of a high end Torch, providing the right environment is the difference between a coral that merely survives and one that truly thrives.
In this guide, we will dive deep into the nuances of caring for these three iconic corals. We will explore the scientific classifications that have recently changed, the precise water chemistry needed to support their stony skeletons, and the delicate balance of lighting and flow that keeps their polyps extended. Managing a reef tank requires patience and a keen eye for detail, especially when dealing with the territorial nature of Euphyllia species. By the end of this article, you will have a thorough understanding of how to place, feed, and maintain these corals to create a breathtaking underwater garden.
Species Identification and Taxonomy of Acans, Torches, and Hammers
Understanding what you are actually putting into your tank is the first step toward successful care. In recent years, the scientific community has reclassified several popular corals, which can lead to confusion for hobbyists. What many still refer to as “Acan Lords” were previously classified as Acanthastrea lordhowensis. However, taxonomists have moved this species into the genus Micromussa, so the correct scientific name is now Micromussa lordhowensis. These corals are known for their fleshy, circular polyps and incredible color variations, often featuring concentric rings of red, green, blue, and orange. They are colonial corals that grow by encrusting over rockwork, creating a dense mat of colorful “heads.” Other species like Acanthastrea echinata remain in the Acanthastrea genus and are known for being much more aggressive and having a flatter, more interconnected fleshy appearance.
The Torch coral, Euphyllia glabrescens, is perhaps the most iconic of the “fleshy” LPS corals. It is characterized by long, thin tentacles that end in a small, often contrasting colored tip. These tentacles sway rhythmically in the water current, resembling a flickering torch. Torches are branching corals, meaning they grow a central stony skeleton that splits into individual stalks, each topped with a single large polyp. Because of their long tentacles, they occupy a significant amount of vertical and horizontal space in the water column.
Hammer corals come in two primary growth forms: branching and wall. The branching hammer, Euphyllia paraancora, grows similarly to the torch, with individual heads that can be fragged or separated easily. The wall hammer, Euphyllia ancora, grows a single, continuous, meandering skeleton that does not branch. Both types feature tentacles with T-shaped or anchor-shaped tips, which is where they get their name. A closely related cousin often found alongside hammers is the Frogspawn coral (Euphyllia divisa), which has multi-tipped tentacles that look like a cluster of grapes. Identifying whether your hammer is a wall or branching variety is crucial, as wall hammers are generally considered more difficult to keep and much harder to fragment without causing lethal damage to the specimen. According to the World Register of Marine Species, these classifications are vital for understanding the natural habitats and biological needs of these animals.
Mastering Water Chemistry for LPS Corals
Maintaining stable water chemistry is the foundation of reef keeping. Because Acans, Torches, and Hammers are stony corals, they require specific minerals to build their calcium carbonate skeletons. If these levels drop too low, growth will stall, and the coral may begin to recede from its skeleton. The four most important parameters to monitor are salinity, alkalinity, calcium, and magnesium.
Salinity should be kept at a natural seawater level of 1.025 to 1.026 specific gravity. Stability is more important than the specific number, so using an auto top off (ATO) system to replace evaporated water with fresh RO/DI water is essential. When it comes to the “big three” minerals, alkalinity is the most critical for LPS corals. We recommend keeping alkalinity between 8.0 and 11.0 dKH. A sudden swing in alkalinity is one of the leading causes of “brown jelly disease” or rapid tissue necrosis in Euphyllia. For precise measurement, the Hanna Marine Alkalinity Checker is a favorite among hobbyists for its digital accuracy.
Calcium levels should be maintained between 420 and 450 ppm. Calcium is the building block of the skeleton, and while LPS corals do not consume it as quickly as small polyp stony (SPS) corals, they still need a consistent supply. Magnesium acts as a buffer that allows you to maintain high levels of calcium and alkalinity without them precipitating out of the water. Magnesium should be kept between 1300 and 1400 ppm. To keep track of these levels, a comprehensive kit like the Red Sea Reef Foundation Pro Test Kit is invaluable. For a broader look at your tank’s health, including nitrates and phosphates, the Salifert Master Reef Testing Combo Kit provides professional grade accuracy for various essential parameters.
Nutrient levels (nitrates and phosphates) are also vital. Unlike some SPS corals that prefer “ultra low” nutrient environments, Acans and Euphyllia generally thrive in “dirtier” water. Nitrates between 5 and 15 ppm and phosphates between 0.03 and 0.10 ppm provide the organic material these corals need to stay fleshy and vibrant. If the water is too clean, Acans may lose their puffiness and Torches may appear thin or retracted.
Lighting and Flow Requirements
Lighting and flow are the two environmental factors that you will spend the most time adjusting. Each of these corals has a “sweet spot” that allows for maximum polyp extension and photosynthetic efficiency. Acans (Micromussa lordhowensis) generally prefer lower to moderate light. In the wild, they are often found in deeper water or shaded areas. A PAR (Photosynthetically Active Radiation) range of 75 to 150 is usually ideal. If the light is too intense, the colors may bleach, or the coral may remain tightly retracted. If you notice your Acans looking flat and thin, they might be getting too much light.
Torches and Hammers prefer moderate light, typically in the 150 to 250 PAR range. They rely heavily on their symbiotic zooxanthellae for energy, so adequate lighting is necessary for growth. However, high end “Holy Grail” or “Gold” torches are particularly sensitive to light changes. It is always better to start these corals lower in the tank and slowly move them upward over several weeks to acclimate them to your lighting schedule.
Flow is equally important but often misunderstood. For Euphyllia (Torches and Hammers), the goal is “moderate, chaotic flow.” You want the tentacles to sway gently in the breeze, not be blasted in one direction. Direct flow from a powerhead can tear the delicate flesh of a Torch or Hammer against its own sharp skeleton, leading to infection and death. If the tentacles are retracted or flattened against the skeleton, the flow is likely too strong. Acans, on the other hand, prefer lower flow. They need just enough movement to keep detritus from settling on their fleshy polyps, but not so much that they cannot expand. When an Acan is happy, it will look like a puffed up marshmallow. For more detailed strategies on where to put these corals, check out our Coral Placement Guide.
Feeding and Nutritional Needs
While these corals get a significant portion of their energy from light, they are also active predators. Feeding your Acans, Torches, and Hammers can significantly increase their growth rate and improve their coloration. Acans are particularly greedy feeders. If you observe them at night or shortly after adding food to the tank, you will see their feeding tentacles extend from the edges of each polyp. They love meaty foods like mysis shrimp, brine shrimp, and specialized LPS pellets. Target feeding an Acan colony once or twice a week with a pipette can result in much faster head splitting and growth.
Torches and Hammers also benefit from feeding, though they can be a bit more finicky. They have a central mouth in each head. You can offer them small pieces of seafood or liquid coral foods. Many reefers use amino acid supplements, which are absorbed directly from the water column and can help with tissue repair and vibrancy. When feeding, it is important to turn off your powerheads for 10 to 15 minutes to allow the corals to grasp the food and move it toward their mouths without it being washed away.
Be careful not to overfeed. Any uneaten food will rot and contribute to nitrate and phosphate spikes, which can lead to nuisance algae growth. A balanced approach of broadcast feeding the whole tank with powdered foods and target feeding specific colonies with meaty bits is usually the most effective strategy. If you are new to this, our guide on LPS Corals for Beginners covers some of the easiest feeding methods to get you started.
Managing Aggression, Pests, and Diseases
One of the most challenging aspects of keeping these corals together is managing their personal space. Corals may look stationary, but they are constantly engaged in chemical and physical warfare for reef real estate. Torches are the undisputed kings of aggression in the Euphyllia world. They possess “sweeper tentacles,” which are specialized, extra long tentacles packed with stinging cells called nematocysts. These sweepers can extend several inches beyond the normal polyp extension, stinging and killing any neighboring corals that get too close.
Hammers are also aggressive but generally less so than Torches. Interestingly, most species within the Euphyllia genus (Hammers, Frogspawn, and Grape corals) can usually touch each other without stinging. However, Torches are the exception; they will often sting Hammers or Frogspawn if they come into contact. Therefore, it is safest to keep Torches isolated from other corals.
Acans are a different story. While they do not have long sweeper tentacles, they can deploy “mesenterial filaments,” which are essentially their stomach linings, to digest neighboring corals that touch them. They are particularly vulnerable to being stung by Euphyllia. If a Torch tentacle brushes against an Acan, the Acan will likely suffer tissue loss or “melting” in that area. Always leave at least 4 to 6 inches of space between different types of corals to account for growth and tentacle extension. This spacing is vital for the long term health of your reef, as a single night of “coral war” can wipe out an expensive colony.
Even with perfect parameters, you may encounter health issues with your corals. The most dreaded disease for Euphyllia is Brown Jelly Disease (BJD). This is a rapid bacterial or ciliate infection that turns the coral’s flesh into a brown, jelly like goo. It can consume an entire head of a Torch or Hammer in hours and can quickly spread to other heads or nearby colonies. If you see BJD, the best course of action is to immediately remove the affected coral and siphon out the jelly to prevent it from floating onto other corals. Some hobbyists have success with specialized dips or antibiotic treatments in a separate quarantine tank, but BJD is often fatal.
Acans are generally hardier, but they can suffer from “Acan eating spiders” or flatworms. These pests are tiny and difficult to see, but they will cause the coral to stay retracted and slowly lose color. Dipping any new coral in a pest control solution before adding it to your display tank is the best way to prevent these issues.
Another common problem is tissue recession, where the flesh of the coral begins to pull away from the stony base. This is usually caused by a sudden change in alkalinity, poor water quality, or physical damage from high flow. If you notice recession, check your parameters immediately. Stability is the key to recovery. If the water is clean and stable, the coral may regrow its tissue over time, but it is a slow process. Keeping a close eye on the “puffy” appearance of your Acans and the “fullness” of your Euphyllia will help you spot these problems before they become catastrophic.
FAQ: Frequently Asked Questions
Where is the best place to put an Acan in my tank?
Acans should generally be placed in the lower third of the aquarium. They do exceptionally well on the sand bed or on low lying rocks. Placing them on the sand bed allows them to expand their fleshy polyps without being restricted by neighboring rocks. However, you must ensure that your sand sifting fish or snails do not constantly bury them in substrate, as this can irritate the tissue and lead to infections. If you have a high par lighting system, you might even consider placing them in a slightly shaded area under an overhang. They prefer a low to moderate flow environment where they can gently “puff up” during the day.
Why is my Torch coral not extending its tentacles?
A retracted Torch coral is a sign of stress, and there are several potential culprits. First, check your flow. If the flow is hitting the coral directly from one side, it will retract to protect its delicate tissue from being torn against the skeleton. Second, check your water chemistry, specifically alkalinity. Even a small swing in dKH can cause Euphyllia to pull back. Third, look for physical irritants. Are there snails crawling on it? Is a neighboring coral stinging it? Lastly, check for pests like flatworms or signs of Brown Jelly Disease. If the coral looks healthy otherwise but is just retracted, it may simply be acclimating to a change in lighting or a recent water change.
Can Hammer corals and Frogspawn corals touch each other?
Generally, yes. Most branching and wall Hammers (Euphyllia ancora and paraancora) can touch Frogspawn (Euphyllia divisa) and Grape corals without any issues. They are closely related and their stinging cells do not seem to trigger an aggressive response in one another. This allows reefers to create “Euphyllia gardens” where different colors and textures of Hammers and Frogspawn are clustered together for a stunning visual effect. However, you should still be cautious when introducing a new specimen, as there are occasionally “grumpy” colonies that may react poorly. Note that Torch corals should almost never be allowed to touch Hammers or Frogspawn, as the Torch is significantly more aggressive.
Conclusion and Next Steps
Caring for Acan, Torch, and Hammer corals is one of the most rewarding experiences in the reef aquarium hobby. These corals bring a level of movement and color that is hard to match with any other species. By focusing on the fundamentals - maintaining stable alkalinity, calcium, and magnesium; providing moderate, chaotic flow; and ensuring proper spacing to avoid aggression - you can create an environment where these animals will thrive for years. Remember that patience is your best tool. Avoid making drastic changes to your tank, and always acclimate new corals slowly to your lighting and water conditions.
As you become more comfortable with these species, you will start to recognize the subtle signs of their health, from the way an Acan extends its polyps for food to the rhythmic sway of a healthy Torch. These corals are not just decorations; they are complex animals that respond to their environment in fascinating ways. Keep your water clean, your lights adjusted, and your feeding consistent, and you will be well on your way to a master level reef display.
The key to long term success with LPS corals is precision. If you haven’t already, invest in high quality testing equipment to ensure your parameters stay within the ranges discussed today. Monitoring your alkalinity and calcium daily when first adding these corals will help you understand their consumption rates and keep your tank stable.
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