Purple Tipped Acropora

Table Top Coral, Tabulate Acropora, Cluster Coral

Family: AcroporidaePurple Tipped Acropora, Acropora tenuisAcropora tenuisPhoto © Animal-World: Courtesy Greg Rothschild

   The Purple Tipped Acropora is one of the more affordable Acros, yet its beauty is priceless!

   The Purple Tipped Acropora Acropora tenuis, also known as the Table Top Coral or Tabulate Coral, is usually cream colored with purple tips. They can also be blue, purple, cream or brown with blue or cream tips, dark red or other bright colors. All the variations in hybrid colors are too numerous to count! The corallites at the tips have a rosette pattern when viewed from above.

   The Purple Tipped Acropora is easily recognized, though they do show variations based upon their geographic location. Specimens found in the western Indian Ocean and the Red Sea have relatively thin and rounded corallite walls. They are easy to frag, and once established they grow fast, so a very large aquarium is suggested.

   Acropora corals are some of the largest, most contributing corals for reef formations in the world. In fact, between the Acropora and Montipora corals, they make up one-third of all reef building coral species. In the wild they are the most tolerant of water temperatures, salinity changes, water movement, and lighting, but in captivity they can prove to be very difficult to keep. In the ocean, they are the first to arrive at a reef and spread quickly. Other corals that arrive later, then tend to move in.

   The A. tenuis have been propagated in captivity thus helping to spare wild populations in the world's reefs. Buying captive propagated A. tenuis helps the aquarist, since they are a little more hardy than their wild siblings, but they can still succumb to diseases typical to Acros.


Geographic Distribution
Acropora tenuis
Data provided by GBIF.org
  • Kingdom: Animalia
  • Phylum: Cnidaria
  • Class: Anthozoa
  • Order: Scleractinia
  • Family: Acroporidae
  • Genus: Acropora
  • Species: tenuis
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Scientific name

   Family: Acroporidae
   Species: Acropora tenuis

Distribution / Background

   Acropora Coral Information: The Purple Tipped Acropora Acropora tenuis was described by Dana in 1846. They are in what is called the selago group of Acros that include A. selago, A. donei, A dendrum, and A. yongei. Their corallites have flared or pointed lower lips. Some of their growth forms have been included in common names such as Table Top Coral, Tabulate Acropora, Purple Tipped Acropora, and Plate Coral. They show variations based upon their geographic location. Specimens found in the western Indian Ocean and the Red Sea have relatively thin and rounded corallite walls.

   Where Acropora Corals Are Found: The Acropora tenuis are found in the Pacific and Indian Oceans and the Red Sea. They are found from Mauritius, east to the Marshall Islands, Coral Sea and the Elizabeth and Middleton Reefs in the east, and Australia's Great Barrier Reef as well as the Houtman Abrolhos Islands on Australia's west coast.

   Acropora Coral Habitat: The A. tenuis are found on upper reef slopes where the current is very strong. 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.

Status

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

Description

   What do Acropora Corals look like: All Acropora Spp. corals have very porous and lightweight skeletons. The Purple Tipped Acropora A. tenuis has evenly spaced branches and radial corallites that are long and tubular. These look like sideways "C"s connected to the branch. Their corallites have flared or pointed lower lips, giving them a rosette pattern when viewed from above. They come in cream, blue, purple, or cream with purple tips and other bright colors.

Purple Table Top Coral - Acropora tenuisTable Top Coral - purple color Photo © Animal-World:
Courtesy David Brough

   These corals are characterized by fast growing terminal (or axial) polyps at the tips of the branches. The polyps at the tips secrete this corallite, constantly forming new growth in a cluster shape. 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.

   Their radial corallites (the cup formed by a polyp) are found in two sizes. The larger ones are in rows and increase slightly in size towards the base of the branches. The appearance is a neat cluster look with a "ball" like shape arrangement. This growth is necessary since the A. tenuis is found in very turbid water. At times, this coral is exposed to the air at low tide.

   Acropora Coral Life Cycles: The Purple Tipped Acropora A. tenuis 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. tenuis 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 Levels Prefers Medium Lighting Levels Prefers High Lighting Levels
Water Flow: Prefers Low Water Flow Levels Prefers Medium Water Flow Levels Prefers High Water Flow Levels
Temperament: Peaceful Temperament Semi-Aggressive Temperament Aggressive Temperament

   A typical live rock/reef environment is what is needed for your Purple Tipped 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: High, metal halides are suggested.
  • Temperature: 74° - 83° F (23° - 28° C)
  • Salinity / Specific Gravity: 1.024 to 1.025
  • Water Movement: Moderate to strong. They prefer a strong, random, mixing-type current, therefore a rotating powerhead or wavemaker setup is recommended.
  • Water Region: Middle 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

   Acroporas 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 sea stars and others from the same genus are known to eat Acropora.

Availability

   Acropora Corals for Sale: The Purple Tipped Acropora A. tenuis 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.

References

Author: Elizabeth M. Lukan; Clarice Brough, CRS; Carrie McBirney

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