How to Care for Acan Corals

How to Care for Acan Corals

How to Care for Acan Corals

Acan Corals or Acans (Micromussa lordhowensis) are a group of large poly stony (LPS) corals that are very popular in the reef aquarium hobby because of their vivid color combinations, hardiness, and ease of care.

Acans are also renowned for their fast growth rate, tolerance, and the ability to easily adapt to a new reef environment. All these remarkable features make it an excellent choice for reef hobbyists.

This guide provides an insight about Acan corals and how you can care for them in reef tanks.

Quick Notes about Acan Corals

Name Acan corals
Other Names
Acan Lords, Micro Lords
Scientific Name Micromussa lordhowensis (previousely Acanthastrea sp.)
Tank size (minimum) 10 gallons (~40 liters)
Keeping Easy to moderate
Propagation Easy
Low to Moderate
Water flow Low to Moderate
Optimal Temperature 23 – 26°C  (~74°F – 80°F)
Optimal Salinity SG = 1.023 – 1.025
Optimal PH 8.1 – 8.4
Optimal KH 8 – 12
Nitrate Less than 10 ppm
Feeding Photosynthetic
Tank placement Bottom
Growth Rate Fast
Invasive No
Aggressiveness Peaceful 
Color Form Red, purple, grey, blue, green, brown, pink, orange, etc.

Origin of Acan Corals

There is a lot of confusion about the origin and taxonomy of Acan corals. Up until a few years ago, they were scientifically classified and referred to as Acanthastrea genus which included 8 species.

However, according to a new study, scientists concluded that Lordhowensis specie was much closer related to other corals of Micromussa genus rather than the corals of Acanthastrea genus. Therefore, they reclassified it to Micromussa Lordhowensis.

The problem, though, that everybody in the hobby got used to the old name. So, do not be surprised to see the old name here and there for years to come.

Kingdom: Animalia (The Animal Kingdom which consists of multicellular eukaryotic organisms).

Phylum: Cnidaria (A phylum under Kingdom Animalia which contains over 11,000 species of aquatic animals found in both freshwater and marine environments, a larger percentage are marine).

Class: Anthrozoa (A class of marine invertebrates which includes the sea anemones, stony corals, and soft corals).

Order: Scleractinia (They are known as stony corals or hard corals, the individual animals are fondly known as polyps and have a cylindrical body crowned by an oral disc in which a mouth is fringed with tentacles).

Family: Lobophylliidae (A family of large polyp stony corals. The family was created in 2009 after a revision of the robust families of Faviidae, Merulinidae, Mussidae, and Pectiniidae).

Genus: Acanthastrea & Mircromussa

Habitat of Acan Corals

Acan corals are commonly found in reef environments. They usually occur in the western Indo-Pacific in reefs at depths of about 0 – 30 m (0 – 98 feet) or more.

Their geographical distribution ranges from the Red Sea, Gulf of Aquaba, the eastern coast of Africa to the East China Sea, Most parts of Australia, and the Solomon Islands.

Interesting fact: The most common and popular Acan species Mircromussa Lordhowensis takes its name from Lord Howe Island, they are also found around Australia in the Flinders Reef, Elizabeth Reef, Middleton Reef, Dampier Archipelago, and the Burrup Pennisula.

Description of Acan Corals

Acan Corals or Acans (Micromussa lordhowensis)
Check out some amazing photos on

In nature, Acan corals colonies are massive and usually flat, reaching 2 – 3 meters in diameter. Each coral has a calcium skeleton (collarites) beneath soft fleshy polyps.

The collarites is a skeletal cup, formed by an individual stony coral polyp, in which the polyp sits and can retract into. It can be up to 15 mm (0.6 inches) in diameter. The septa are thick near the wall of the collarite and have tall fine teeth.

Acan corals come in varying color combinations and patterns, for instance, the Lordhowensis specie is often composed of two or more contrasting shades of red, orange, purple, pink, blue or green.

Behavior of Acan Corals

Polyps from the genus Mircromussa are generally peaceful towards other coral species, they do extend tentacles in order to feed and can damage other corals. Therefore, they should be properly distanced or kept away from other corals. These corals will extend their stomachs at night to attack corals nearby.

Acans grow by producing new heads and they will eventually form a dome shape when fully grown. In some cases, they are known to grow rapidly that they sprout a new head every 7-14 days once feeding needs are met and optimal water parameters are maintained.

Feeding Acan Corals

Just like other animals in the class Anthrozoa, Acan corals receive a great portion of their nutrition through photosynthesis from their symbiotic relationship with the zooxanthellae algae. In a well-established reef aquarium, Acans can also feed through the water column by consuming the phytoplankton and zooplankton suspended in the tank water.

However, regular feeding should be a priority, they should be fed every 2 or 3 days.

Acans are more active at night when your fish are asleep. They will extend their tentacles to collect meals. You can feed them at any time of the day regardless, Acans will accept the following meals:

Note: Bear in mind that corals newly introduced to the tank may not accept food for a while, this is quite normal, they will only commence feeding when they have fully acclimated and settled in their new environment.

Lastly, it is advisable to practice target feeding to ensure that Acan corals are well fed, this can be achieved using a turkey baster or pipette to accurately direct the meal to their heads. Do not forget to turn off your pumps for easier target feeding.

Tip: Spray Acan corals with a trace amount of food to initiate their feeding response after a few minutes. Once they feel the food they will open up their feeding tentacles to consume the food.

Tank Requirements and Parameters

Tank size:

For the tank size, I would recommend large tanks starting from 20 gallons (80 L). In this case, the reason for large tank capacities is stability; housing Acans in larger tanks allows for more water volume which promotes stability of the water chemistry.

If you cannot afford /maintain that, then you can opt for a smaller 10-gallon tank (~40 L). However, as long as you have stable water parameters it is possible to keep them in any tank.

Water type, Temperature, Hardness, and pH:

Temperature: The water temperature should be between 74° F – 80° F (23° C – 26° C) to ensure healthy growth and development.

pH: The ideal pH level is between 8.1 – 8.4. This can be easily increased using a buffer.

Hardness: The ideal kH value for a marine aquarium is between 8-12 dkH (3 – 5 meg/l). A low kH can easily be corrected by adding Seachem Reef Carbonate or Reef builder.

API REEF MASTER TEST KIT – link to check the price on Amazon


Acans corals do best under low – moderate lighting (20 – 50 PAR)heavily influenced by the blue spectrum in the 20,000 Kelvin range. This will make their colors come to life!

Avoid strong lighting, depending on the species, it may prevent the polyps from opening up fully, cause the loss of coloration, or even worse – bleach them.

Lighting has also a major impact on color. For example, high light can even cause a loss of blue pigments and a deepening of red pigments. Be ready that the coloration of Acans corals in the store will be different in your set up.


Water movements or flow should be low – moderate. Preferably closer to the lower side.

However, avoid dead spots in your tank. High flow can also prevent your corals from opening and might make it more difficult to feed them.

In addition, you need enough indirect water movements to enable them filter-feed, remove waste products, and to ensure that debris doesn’t collect on the Acans corals. This is best achieved using a wavemaker or alternating powerheads that create laminar flow within the tank.

Whichever decision you take, always remember that moderation is key!

Care and Maintenance of Acan Corals

Water changes of 20% a month, 10% bi-weekly, or 5% weekly is needed for tanks housing Acans. A 5% weekly water change is essential for majorly nano reef tanks, this replenishes many of the needed additives and it is cheaper than purchasing additives for the tank water.

Monitor your Acans corals on a regular basis, that way you can easily discover and tackle any problem that arises quickly.

Acan corals will appreciate standard saltwater parameters, they won’t tolerate high drastic changes in water chemistry regardless of their hardy nature. A high standard of water quality is key to a healthy and successful marine aquarium. Lots of health and algae problems are caused by unstable water quality.

The following water parameters should be properly maintained, these parameters can always be tested with accurate test kits obtainable at pet stores.

  • Salinity: 1.023 – 1.025 (The measure of total dissolved salts measured as specific gravity).
  • Phosphate: 0.02 – 0.05 ppm
  • Nitrate: <10 ppm
  • Calcium: 380 – 450ppm. Calcium is a building block for corals and it is vital for longevity. It can be maintained by adding calcium supplements.
  • Magnesium: 1200 – 1350ppm. Magnesium is important for coral growth, as well as maintaining water pH.
  • Strontium: 8 – 10 ppm

Note: Acan corals are pretty sensitive to phosphate levels in the tank. Once you get too much (0.1 and more), they often shrivel up. In this case, do a water change and stop feeding them for a week. They should open back up gradually.

Placement in the Tank

Placement of your Acan corals can greatly affect its growth potentials. They can be placed on the tank bottom, sand bed, or on live rock, the placement position can either enhance or inhibit how the colony will grow out.

It has been duly observed that keeping an Acan on the tank bottom gives it a ball shape, but this significantly limits its growth rate.

Furthermore, placing the Acan corals on the sand bed can be detrimental, because, in the advent of high water movements, sand can get trapped in between the skeleton and tissue leading to their demise.

On the other hand, if the coral is fastened to a live rock, it will grow out uniformly in accordance to the shape. The coral has a huge potential of getting larger when placed on a large live rock.

Fragging and Propagation Acan Corals

Large poly stony corals including Acans corals are hermaphrodites, meaning that they possess male and female gametes within the same organism, and they can also reproduce both sexually and asexually.

Acans corals are broadcast spawners, in the wild, they reproduce by releasing eggs and sperm at the same time which results in a fertilized egg, this develops into a free-swimming planula larva. After a while, the larva will settle onto the substrate, becoming planksters.

Eventually, the larva will metamorphose into a tiny polyp which begins to excrete calcium carbonate, thus developing into a coral.

Note: Planula larva are extremely vulnerable to predation, therefore, very few are likely to survive.

In captivity, Acan corals will reproduce by dropping tissue when stressed, in an attempt to propagate. Asides that, they can also be propagated by fragmenting or cutting.

This process is simple, but you have to be cautious.

  1. You should ensure your hands are clean or wear a pair of gloves.
  2. Take out each polyp and cut down the center of the polyp, this can be done through the mouth and they can be cut into halves or quarters. Cutting can be done using a sharp scalpel, blades, bone cutters, diamond band saw or dremel. Actually, this is the most difficult part. Acan corals are very hard to break clean! Be very careful, you do not want to shatter the skeleton of the coral!
  3. Try to cut around all of the ‘eyes’ of the Acan corals. If you cut through them those parts (eyes) will most likely
  4. Afterward, treat the new frags with an iodine solution (for example, Lugol’s solution) to prevent them from contracting diseases, then you can attach them to a live rock before placing them back into the tank.
  5. Glue the piece to a frag plug.
    Tip: Take a frag plug and put it in the water for a couple of minutes to release the air bubbles that might be in the ceramic frag plug.

Things that you might need depending on your method:

Coral Fragging Kit tools. Profile - Vermetid snails. How to remove them


 Coral Propagation Fragging Kit Set (link to Amazon)

Acan corals grow pretty fast. It is not uncommon to notice new heads forming only a few weeks after cutting a new frag. If there is no space left, the growth rate slows down and they start growing by excreting more skeleton and mounding into a larger shape.

Problems associated with Acan Corals

Coral bleaching: Acan corals bleaching is a condition whereby the coral’s flesh becomes translucent or pale, making the skeleton to become visible through the coral’s tissue. Bleaching occurs when the symbiotic algae known as zooxanthellae found in almost all living coral tissue is lost / expelled from the coral.

In addition, partial bleaching also exists whereby some of the zooxanthellae are lost. The partial loss of zooxanthellae affects growth rates and overall health of the Acan corals, therefore leaving it susceptible to diseases.

Certain factors that can cause bleaching include increase in lighting (excessive lighting), high water temperature and extreme changes to salinity amongst many others.

Yellow blotch disease: This disease is characterized by the presence of circular spots of translucent tissue with a yellow color tone or the appearance of a narrow band of pale tissue at the base of the Acan coral. While these signs are present at a particular part, other surrounding areas will remain healthy and normal, as well as retaining their natural coloring.

Yellow blotch disease is caused by a type of bacteria that causes pale yellow lesions and attacks/kills the zooxanthellae algae within the coral, thus eliminating the coral’s ability to perform photosynthesis efficiently.

White pox: White pox is caused by a gram-negative bacteria called Serratia marcescens. In this condition, the Acan coral will exhibit white spots on its surface. These spots increase in number and size as the bacteria starts to spread and consume the coral’s tissue.

Acan Corals and Tankmates

Acan corals are generally considered reef safe.

There are some reports that Camel shrimp and Peppermint shrimp have a reputation for attacking these corals.

However, when I was writing the article about this specie I came across an interesting study that instead of Lysmata wurdemanni (the Gulf and Carribean Peppermint shrimp), people often get the Atlantic Peppermint shrimp (Lysmata boggessi).

Unfortunately, Atlantic Peppermint shrimp (Lysmata boggessi) is not reef safe.

Buying Acan Corals

Without a doubt, identifying and buying Acan corals especially the Acan Lord (Micromussa lordhowensis) can be a bit tasking. It would be easier to identify Acan corals if the fleshy polyps are out fully.

This helps to avoid confusion with Favites and Favia. Unlike these other corals, the corallite walls of M. lordhowensis are not separate on its skeletal structure, rather all its walls are shared between the individual polyps.

When searching for healthy specimens, be on the look out for Acans with a fluffy appearance and bright colors, that way you are sure of obtaining an unbleached coral.

Acans can be purchased at pet stores and online through pet retailers. The cost of these corals varies depending on the rarity, retailer, color, and size. Prices are fair – $20 or less for a one or two heads poly frag. However, some rare color variations can cost up to $100 or so.

In Conclusion

Acan corals are wonderful animals, they are one of the most popular and relatively undemanding choices when it comes to beginner reef aquarium species.

These large poly stony corals possess a unique structure, variety of bright color patterns and combinations that will definitely be a centerpiece of any reef tank and excite your reef tank viewers.

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How to Care for Acan Corals or Acans (Micromussa lordhowensis)

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