Acropora formosa the Staghorn Acropora or Staghorn Coral
Staghorn Acropora

   The Staghorn Acropora is not only fast growing, it’s easy to frag and one of the ‘beginner’ Acropora!

   The Staghorn Acropora Acropora formosa is what is considered as a beginner’s Acropora. They are easy to propagate once they are established. Because no two aquariums are exactly alike, this intriguing coral will grow in a slightly different pattern in each individual tank. This is due to different water flow and lighting. Aquarist will find a little tidy profit from fragging this fast grower if they are so inclined!

   Acropora formosa is a branching or arborescent acropora. It is a staghorn type of branching acropora, hence its most popular common name. Those found in shallow water have short and compact branches and specimens found in deep water have more open branches.

   The Staghorn Acroporas have been propagated in captivity, thus helping to spare wild populations in the world’s reefs. It is considered a favorite of reef aquarists (per Eric H. Borneman in Aquarium Corals: Selection, Husbandry, and Natural History). Buying captive propagated A. formosa helps the aquarist, since they are a little more hardy than their wild siblings, but they can still succumb to diseases typical to Acros.

  • Kingdom: Animalia
  • Phylum: Cnidaria
  • Class: Anthozoa
  • Order: Scleractinia
  • Family: Acroporidae
  • Genus: Acropora
  • Species: formosa

Scientific name

   Family: Acroporidae
   Species: Acropora formosa

Distribution / Background

   Acropora Coral Information: The Staghorn Acropora Acropora formosa was described by Dana in 1846. It is a member of what is called the formosa group of Acros. Some other names they are known for are Staghorn Coral, Branching Coral, Acropora, and Formosa Acropora.

   Where Acropora Corals Are Found: The Acropora formosa are found in the Pacific and Indian Oceans, and the Red Sea; in Fiji and the Sulu Sea. They are found from Madagascar to the Phoenix and Marshal Islands, and in Australia’s reefs.

   Acropora Coral Habitat: The A. formosa are found on reef slopes and fringes, but are most dominant in lagoons. They are usually in thickets with a single species spreading as far as ten meters (approximately 32.8 feet). They are commonly found along with Acropora nobilis and Acropora grandis with the Staghorn Acropora frequently a dominant species. Some of their growth forms have been included in common names such as Branching Coral or Formosa Acropora.

   In the wild, Acropora spp. corals are found across the reef in various locations from turbid waters (with sediment or foreign particles stirred up or suspended in the water) to those with strong waves and high currents; from areas where there is little light to being fully exposed to the sun (and the air) at low tide.


   The Acropora formosa is on the IUCN Red List for Endangered Species as Near Threatened (NT)


   What do Acropora Corals look like: All Acropora spp. corals have very porous and lightweight skeletons near the edges of the coral and the tips (branches). The bases, on the other hand, are very dense. Acropora formosa, along with the Staghorn Coral Acropora cervicornis, has the densest base skeletons ever recorded in stony corals.They come in mostly cream, but also in brown, blue, pink, and green with pale tips. The most common color is cream to tan with colorful tips.

   The branching Acropora spp. corals are characterized by fast growing terminal (or axial) polyps at the tips of the branches. The tips secrete this corallite, constantly forming new growth that is erratic and thicket-like. These terminal polyps do not have zooxanthellae. They grow quickly because the terminal polyps are fed by the rest of the colony. This allows Acropora to outgrow other corals on the reef.

   Acropora Coral Life Cycles: The Staghorn Acropora A. formosa reaches sexual maturity within 3 to 5 years, with a branch diameter of 1.5-2.75″ (4-7 cm). They can live 4 to 7 years.

Difficulty of Care

   Acropora Coral Care: Acroporas are among the more difficult corals to keep, which is surprising as their natural habitats have a wide array of conditions. In captivity they require stable tank conditions, sudden changes may result in death. They are sensitive to temperature changes, sedimentation, chemical and other environmental stresses. They will stress very easily if the light is too low, or the water movement is not sufficient.

   Acropora need to be carefully acclimated to their new homes. They need to be placed in their permanent position within a tank after acclimation. It takes about 5 to 6 months for the A. formosa to regain their normal growth rates after being added to an aquarium. Moving Acropora from place to place will stress them, and possibly cause death.

   At times a healthy system has an additional Acro added and all the others die from polyp bail out or what people refer to as RTD (rapid tissue degeneration) and a whole tank of acros can be wiped out within a matter of hours. They are unsure why this happens, but it would probably be a good idea to have all the Acros you are going to want, and put them together

Foods / Feeding

   Acropora Coral Feeding: In the wild, Acropora corals have developed several feeding strategies. Through a symbiotic relationship with a marine algae, known as zooxanthellae, they receive the majority of their nutrients. They also capture planktonic organisms and microscopic food particles from the water column and can absorb dissolved organic matter.

   In captivity, feeding zooplankton once a week is the preferred choice. Copepods, Artemia, and nauplii are too large for them to ingest. But new forms of prey are being developed including invertebrate larvae and new strains of rotifers. Many feel that Acros in captivity need to be in a tank that has dissolved or solid organic matter to survive and thrive. Without this, they may seem fine for a while, but over a few months, without any visible indication, they may end up dead because of starvation. Signs of lack of food would be no new growth, polyps extending and some tissue recession.

Aquarium Care

   Excellent and stable tank conditions are required to keep all Acropora spp. corals. Doing water changes of 10% every 2 weeks is needed, although it is suggested that doing 5% water changes once a week will bring about amazing results. Keep the nitrate levels low. Tanks should offer high calcium levels and strontium should be added.

   Suggested levels for Acropora species are:

  • Calcium:  400 to 450 ppm (closer to 450). If the Acro does not have enough calcium, it will not grow. There will be no tissue recession, but the polyps will be extended.
  • Alkalinity:  3.2 TO 4.5 MEQ/L (8 to 10 dKh – 10 is recommended)
  • Phosphates:  0, zero. Phosphates are the worst of all and all corals hate them.
  • Magnesium:  1350-1500. Magnesium makes calcium available, so if your calcium is low, check your magnesium levels before adding any more calcium.
  • Strontium:  10

Aquarium Parameters

Quick Reference Chart
Lighting:Prefers Low Lighting LevelsPrefers Medium Lighting LevelsPrefers High Lighting Levels
Water Flow:Prefers Low Water Flow LevelsPrefers Medium Water Flow LevelsPrefers High Water Flow Levels
Temperament:Peaceful TemperamentSemi-Aggressive TemperamentAggressive Temperament

   A typical live rock/reef environment is what is needed for your Staghorn Acropora, along with some fish for organic matter production. A mature tank (well over a year old) is advised to increase the chance of successfully keeping Acropora.

  • Minimum Tank Size / Length: 100 gallons (380 L) or larger
  • Marine Lighting: Moderate to high/intense, metal halides are suggested.
  • Temperature: 72° – 78° F (22.2° – 25.5° C)
  • Salinity / Specific Gravity: 1.024 to 1.025
  • Water Movement: Moderate to strong. According to Eric H. Borneman in Aquarium Corals: Selection, Husbandry, and Natural History, “… all Acropora seem to prefer a strong, random, mixing-type current …” therefore a rotating powerhead or wavemaker setup is recommended.
  • Water Region: Bottom of the aquarium

Compatibility and Social Behaviors

   The Acropora corals are peaceful, but watch out for crabs. Many experienced aquarists do not believe any crab should be kept in a closed system with Acros. Crabs are opportunistic predators, with the exception some of the symbiotic crabs like commensal crabs, and gall crabs.

   Acroporas are best kept in a small polyp stony (SPS) tank with only other SPS corals. They can send out digestive strands called ‘acontia’ that are actually used to digest neighboring corals, so keep an eye out for any problems. The exception to this would be if your system has an incredible filtration system and the Acros are at least 10″ away from other corals such as zoanthids, large polyp stony (LPS) corals, and other invertebrates.

   Do not keep soft leather corals with your Acropora species as they are aggressive and release terpins that will eventually kill your expensive investment. Leather corals are dangerous to Acros, even in the best filtered aquariums. Some large polyp stony (LPS) corals can stretch out their tentacles and kill your Acros too, so caution is needed if you have a mixed reef.

Sex – Sexual differences

   No sexual difference in appearance is known.

Breeding and Reproduction

   Staghorn type Acropora grow rapidly and are considered to be among the most rapid growing of the stony corals. They will reach sexual maturity within 3 to 5 years, with a branch diameter of 1.5 – 2.75″ (4 – 7 cm). They fragment easily and the fragments can form new colonies. This makes them ideal candidates for captive breeding/propagation.

   The Acropora Spp. are male and female and can reproduce both sexually and asexually. In the wild they reproduce sexually by releasing eggs and sperm at the same time, resulting in a fertilized egg which then forms into a free-swimming planula larva. Eventually the planula larvae settles onto the substrate, becoming plankters. This then forms a tiny polyp which begins to excrete calcium carbonate and develops into a coral. Planula larvae are extremely vulnerable to predation, and very few survive. In the wild Acros reproduce asexually as well. The polyps at the tips of branching species secrete corallite around itself, forming longer branches. Acros also spread from breakage due to storms and fragmentation.

   Propagation is rather simple for Acropora corals. First you need to choose a healthy coral that is not showing any signs of distress. Then, simply cut a branch at least 2″ long and glue the frag to a plug or rock. You can use the 2-part epoxy or underwater putties. A little tip, don’t glue frags upright since they will grow faster on their sides.The slime that the coral will exude should not come in contact with any other corals and gloves are suggested. Give the frag ample water flow.

Potential Problems

   Signs of stress are bleaching and receding and they will diminish and die rapidly. Transporting Acropora spp. corals can be a problem because of their shapes, the easily broken outer edges of the coral skeleton, and the ease with which they become stressed. They are also susceptible to almost every coral disease including white-band disease, black-band disease, necrosis, etc. Acropora is particularly susceptible to rapid tissue necrosis (RTN), especially specimens from the wild.

   For more information on disease see Keeping Acropora Corals: SPS Coral Ailments

   There are many animals that will prey on Acropora spp. corals. Some Acropora have symbiotic relationships with crabs and shrimps that may help them against predators. Other hitchhikers may actually be predators so careful observation must be done. Chocolate seastars and others from the same genus will eat your Acropora.


   Acropora Corals for Sale: The Staghorn Acropora A. formosa can be found easily online and at pet stores, as well as from frag farmers and most reef clubs. Online they can run about $30.00 USD or more depending on size and color.

   Many Acropora spp. corals have been propagated by fragmentation. It is not difficult to find captive-bred colonies of Acropora corals for sale or trade. Captive-bred corals may tolerate less intense lighting and water movement as well as possibly being easier to care for than those taken from the wild.


 Hertshoon (Image Credit: Albert Kok, Wikimedia Commons Public Domain)