Acanthastrea corals, commonly known as acan coral or acan lords, are large polyp stony (LPS) corals and are among the most beautifully colored coral species. They come in purple, red, green, blue, orange, brown, rust, pale tan, and pale grey. The family includes several species with different names, and many tout them as one of the easiest LPS corals to grow. Put the two together, and you have the perfect LPS coral—though with a few quirks to manage.
Table of Contents: Acan Coral Care
With so many corals and patterns available, you’re probably eager to drop down into the various links detailing acan coral care. And that’s up to you—especially if you have experience with LPS corals already. But if you’re new to handling these invertebrates, you might want to read through the entire article and make sure you have a solid handle on things—just to stay on the safe side.
Quick Facts
- Common Names: Acans, Acan lords, Micros, Micro lords, Micromussa
- Scientific Name: Several species, including Acanthastrea echinata and Acanthastrea lordhowensis (now Micromussa lordhowensis)
- Care Difficulty: Moderate
- Coral Category: Large polyp stony (LPS) coral
- Aggression Level: Semi-aggressive. Do not allow other corals to touch, including other acans.
- Expense: Typical LPS price for most common color varieties. Very expensive for popular varieties like Lordhowensis (classified as a Micromussa)
Acan Coral Description
Acan corals are found in the south Pacific, particularly around the Philippines and Hong Kong, in waters down to 30m. In the ocean, acan coral feed mostly at night. However, they acclimate to diurnal schedules in the aquarium and will happily eat when you feed them. Their large, fleshy polyps and vibrant coloration make them a standout in reef aquariums.
Look at the large polyps on this Acan coral frag
Why the name change for the Lordhowensis species? A 2016 study comparing DNA sequences found that Lordhowensis was more closely related to the Micromussa group than the Acanthastrea, prompting a reclassification. Since it’s a relatively recent finding, you can find it listed under both scientific names.
Acan Coral Care
Acan coral is generally hardy and easy to care for, making it a suitable species for intermediate aquarists. Beginners may want to hold off on rushing to pick up a frag—here’s why: Acans are sensitive to placement (light and flow), can be aggressive toward neighbors, require regular feeding for best growth, and are often more expensive than other LPS. These quirks mean they reward attentive care but can frustrate those new to coral husbandry. The amazing color varieties make this LPS a show stopper—even for advanced hobbyists with mature tanks. And since you have flexibility with your tank size (they’ll accept a 5-gallon/19L tank provided you meet their lighting and flow needs), you can set up displays to suit any whim.
But let’s get into the nitty-gritty of that care, shall we?
Acan coral placement
The best placement for an Acan coral is in a location with moderate water flow & light intensity, six inches or farther away from neighboring corals. Too much water flow or light will damage the coral. Acans will damage other corals closer than 6-inches.
One of the most popular questions related to ANY coral care: Where do I place my frags?
The first thing you need to do is make sure you allow for room to grow. Many of us (*raising my hand with a look of guilt*) pack our coral frags in too closely. We optimize the look of our tanks for the present, forgetting to take future growth in mind. Corals are animals, and (when they’re healthy) they colonize available spaces. Not to mention you need to remember that the majority of corals ARE aggressive creatures, bent on defending what (little?) space they have. And since acan coral has some nasty sweeper tentacles, you need to give it plenty of space to prevent turf wars.
You also need to situate this coral in a place with moderate water flow and lighting. (Not too much, not too little—just right) Remember, it IS a large polyp stony coral, and you don’t want the water flow to get so high (like with small polyp stony (SPS) corals) that you end up ripping their delicate flesh.
The same with their lighting needs. If you think about their natural environment, it’s fairly deep—AWAY from the intense sunlight of the surface. If you go for a dramatic lighting scheme to “spotlight” their colors, you’ll cause stress. Actinic lighting will work nicely—and help those vibrant shades pop. A PAR between 25-50 will split the difference between their photosynthesis needs and your desire for a stunning reef tank.
Why are acans sensitive to placement? Acans are especially sensitive to both excessive and insufficient light and flow. Too much light can cause bleaching or tissue recession, while too little can result in dull coloration and poor growth. Excessive flow can damage their fleshy polyps, leading to tissue tearing or retraction, while insufficient flow may allow detritus to settle, increasing the risk of infection.
How to recognize placement issues: Watch for signs such as tissue recession on the side facing the flow, bleaching or fading colors, persistent polyp retraction (especially during feeding times), or uneven inflation of polyps. If polyps remain tightly closed or the tissue pulls away from the skeleton, your acan may be stressed by its environment.
Practical placement framework: Start with a conservative placement: lower in the tank, in moderate indirect light, and in a spot with gentle, variable flow. Observe the coral for at least a week. If polyps are well-inflated and extend during feeding, you’re on the right track. If not, gradually adjust the position—move to a slightly brighter or shadier spot, or adjust flow direction—until you see improvement.
Using your aquascape: Features like rock overhangs, ledges, or caves can help fine-tune placement by providing shade or shelter from direct flow. Tank height and rockwork can also be used to create microenvironments with different light and flow levels, allowing you to dial in the best spot for your acan.
Adapting as your coral grows: As your acan colony expands, polyps may extend into areas with different light or flow, or encroach on neighboring corals. Periodically reassess placement and spacing, and be prepared to move or frag the colony if conditions change or aggression becomes an issue. Tank dynamics evolve over time, so placement is rarely a “set and forget” decision.
Feeding
Acan coral is considered photosynthetic, meaning they derive at least part of their calories from the commensal zooxanthellae that live in their tissue. They also pull some nutrients from the water column. This will help keep nutrient levels in check if you have fish in your tank. However, the amount of nourishment these two processes produce? It isn’t enough to sustain your acans. They’re carnivores. And that means they want MEAT. So you should feed your acans.
When ready to feed, the acan coral will extend its polyps to capture prey: copepods, Artemia, chopped seafood, or even commercial foods (frozen, flake, or pellet). As long as the tentacles can catch something delicious and pull it in, they’ll happily slurp it down. As fast feeders, you’ll find them a fun addition to your tank, too! Once or twice a week, plan to target feed your acans to keep them healthy.
Why target feeding? Target feeding ensures that food reaches the polyps directly, reducing waste and competition from tankmates. Broadcast feeding often results in food being swept away or consumed by other inhabitants before the acan can capture it, especially in tanks with active fish or shrimp.
Risks of overfeeding: Overfeeding can lead to nutrient spikes, fueling nuisance algae or degrading water quality. Uneaten food may accumulate in the substrate or rockwork, increasing the risk of bacterial blooms. Feed only what the coral can consume within a few minutes, and remove excess if necessary.
Signs of effective feeding: Healthy acans will extend their feeding tentacles in response to food, show visible tissue inflation, and gradually increase in polyp number or colony size. If you notice uneaten food, persistent polyp retraction, or a rise in nuisance algae, reassess your feeding frequency and quantity.
Tankmate interference: Some fish, shrimp, or crabs may steal food from acans or nip at their polyps during feeding. To mitigate this, feed after lights out (when fish are less active), use a feeding dome, or distract tankmates with food on the opposite side of the tank while you target feed your acans.
You target feed these aquarium corals by using Julian’s thing to squirt a tiny, gentle blast of food over the polyps. Doubting the importance of feeding these corals? Give it a try. You’ll see your acan coral grow faster with target feeding than broadcast feeding alone. Not to mention the focused feeding will prevent less waste from building up in your tank. (Besides, it’s fun to watch those tentacles extend out to snatch up your offering!)
Compatibility
Acan coral is generally compatible with most other species. The key ingredient to whether they’ll tolerate other coral neighbors is space. If you pack it too close to other corals or allow a green star polyp colony to grow beside them, you’re in for coral warfare. Given enough space to thrive and grow, the acan coral will make an attractive addition to your saltwater aquarium. And the magic number’s 4 inches (10.2cm)—in theory.
Mechanisms of aggression: Acans defend their territory using both sweeper tentacles (which can sting and damage neighboring corals) and chemical warfare (allelopathy), releasing compounds that inhibit the growth of nearby species. These mechanisms allow them to outcompete for space but can lead to losses if not managed.
Given enough space, you can keep them near Plate corals, Favia, Chalices, and other popular corals hanging out in the lower zone of your tank.
But if you plan to keep acans with soft leather corals, you need to take additional measures to neutralize the chemical warfare leathers wage in a tank. Activated carbon and water changes will do the trick, protecting your acan coral from the chemicals the soft corals produce to inhibit coral growth.
Trade-offs in mixed tanks: Mixing acans with other aggressive LPS or soft corals increases the risk of territorial battles. Proactive management—such as regular pruning, using chemical filtration, and maintaining generous spacing—can help minimize aggression. As acans and their neighbors grow, their aggression range increases, so periodic reassessment of layout and spacing is essential to prevent future conflicts.
And then there are the non-coral tank inhabitants you need to consider. You don’t want to keep acans with fish that like to peck at fleshy polyps—and damselfish are some of the biggest offenders. (Unless you meant the acan to be fish food—which is expensive and not recommended) These reef-safe fish will leave your acan coral alone:
Recognizing Signs of Trouble With Acans
Has it been days since you saw your acans’ tentacles extended? An acan coral dying or not happy in the tank because of too much water flow or too much light will not extend its polyps. If your water parameters are good (and stable) and your acan coral still won’t extend its polyps (even at night or even when you attempt target feeding), then it could be the lights or water flow. Carefully move it to an area of lower flow or less intense light (or both, depending on the circumstances).
Other signs of trouble:
- Tissue recession: Tissue pulling away from the skeleton, often starting at the edges, can indicate chronic stress from placement, water quality, or aggression.
- Discoloration or bleaching: Faded or pale tissue may result from excessive light, unstable parameters, or nutrient deficiency.
- Brown jelly disease: A brown, slimy mass covering polyps is a sign of bacterial infection and requires immediate intervention (removal of affected tissue, iodine dip, improved flow).
- Pest predation: Look for bite marks, missing tissue, or visible pests such as nudibranchs or flatworms. Inspect at night with a flashlight if you suspect pests.
- Chemical aggression: Sudden decline or tissue loss near neighboring soft corals may indicate allelopathic warfare. Increase carbon filtration and consider relocating corals.
Diagnostic flow:
- Symptom: Polyps not extending → Likely causes: Excessive light/flow, unstable water parameters, pest irritation → Action: Adjust placement, check water quality, inspect for pests.
- Symptom: Tissue recession → Likely causes: Aggression, chronic stress, poor water quality → Action: Increase spacing, stabilize parameters, improve feeding.
- Symptom: Brown jelly/slime → Likely causes: Bacterial infection → Action: Remove affected tissue, perform iodine dip, increase flow.
- Symptom: Discoloration/bleaching → Likely causes: Excessive light, nutrient deficiency → Action: Reduce light intensity, review feeding and nutrient levels.
Distinguishing problem types: Environmental issues (light, flow, water quality) usually affect the whole colony, while pest or disease problems may start in one area and spread. Chemical aggression often presents as sudden tissue loss near a neighbor. Stable water parameters are critical—acans are sensitive to swings in alkalinity, calcium, and salinity, which can manifest as poor polyp extension, tissue recession, or color loss.
Fragging Acan Coral
Fragging this LPS species is possible and relatively straightforward—as long as you have the right power tools to execute a fast, safe cut. It isn’t a coral I’d recommend for a first fragging experiment, but if you have the right gear (and an iron constitution), it can be done. Acans recover nicely from the process—particularly when you’ve been target feeding them to encourage healthy growth.
Why are acans more challenging to frag? Acans have a thick, stony skeleton and fleshy polyps that can be easily torn or damaged during cutting. The polyps often grow closely together, making it difficult to separate them cleanly without injuring tissue. Mistakes can lead to polyp loss, infection, or slow recovery.
So what tools do you need?
- An iodine bath (to prevent any infection)
- A bandsaw
Common fragging mistakes: Cutting too slowly (causing tissue tearing), using dull tools, or failing to retract polyps before cutting can all increase the risk of damage. Inadequate post-fragging care—such as poor water quality or insufficient flow—can lead to infection or tissue loss.
Post-fragging care: After fragging, observe the new frags for signs of stress or infection. Place them in low to moderate flow, away from aggressive neighbors, and maintain stable water parameters. Target feeding can help speed recovery. Watch for healthy tissue regrowth over the cut edge and polyp inflation. Signs of trouble include persistent tissue loss, brown jelly, or failure to inflate after several days.
It sounds frightening (and complicated), but it isn’t terribly difficult—provided you make sure those polyps are safely retracted.
Finding Acans
Acans are popular and available at most above-average local fish stores. It’s also easy to purchase them from online stores, like LiveAquaria and others.
Types
Due to their popularity and the mind-numbing array of color choices, you’ll find different types or varieties available under different names. For instance, you’ll see names pop up like Australian Lord (or Aussie Lord), rainbow, green, Superman, etc. If you’re looking for a specific type or coloration to fit your tank, I recommend you turn to online stores so you can find the precise color and pattern you’re looking for.
How to choose a healthy acan:
- Look for well-inflated, plump polyps with no visible tissue recession or skeleton showing.
- Color should be vibrant and even—avoid specimens with pale, bleached, or patchy tissue.
- Check for polyp extension in response to light or gentle flow; healthy acans will often react to stimulus.
- Avoid frags with torn tissue, brown jelly, or excessive mucus.
- Be cautious with freshly imported or recently fragged acans, as they may be stressed and more prone to disease.
For More Information
As you can see from the information on this page, caring for acan coral takes moderate skill. You need to provide the right aquarium conditions (water parameters), lighting, and flow. You also need to pay attention to the range of those sweeper tentacles, so you don’t end up with a coral battle within your reef tank. And since they can be a relatively expensive species to purchase, it’s recommended that you wait to pick out your first specimen until after you’ve mastered a few of the other more common and hardy LPS species.
If you enjoyed reading about the acan coral, you should read about these other popular LPS coral species:
Reference
Borneman, Eric H. Aquarium Corals. Microcosm Ltd; 1st Printing Edition. (March 1, 2001)