Animal-World > Aquarium Coral Reefs > Gorgonians > Splendid Knotted Fan Coral

Splendid Knotted Fan Coral

Pacific Sea Fan, Knotted Fan Coral, Red Gorgonian

Family: MelithaeidaeSplendid Knotted Fan Coral Acabaria splendens, also known as Pacific Sea Fan, Knotted Fan Coral, Acabaria Fan Coral, Acabaria Sea Fan, and Red GorgonianAcabaria splendensPhoto © Animal-World: Courtesy David Brough

   The Splendid Knotted Fan Coral is a rarity in the aquarium industry, and a hard to keep beauty!

   The Acabaria corals are found in the Red Sea, Indo-Pacific, Indian Ocean, and the Maldives. They inhabit reef crests, current swept slopes, and calm open water; but live along shaded areas or under overhangs and in dimly lit caves. They are very colorful! The attraction of these sea fans is the deep red or deep orange color of their rind contrasted behind light polyps. They also have fascinating twists and turns in their branches.

   Commonly referred to as a Gorgonian Sea Fan or just Sea Fan, the Acabaria genus have a dichotomous structure, which is a random "Y" shaped branch pattern. Species like the Red Reef Crest Gorgonian A. biserialis and Crossland's Fan Coral A. crosslandi branch across one plane, creating a fan-shaped colony. However others, like the Splendid Knotted Fan Coral A. splendens and the Delicate Net Fan A. variabilis, are only roughly fan shaped, as you can see in the picture above.

   The Splendid Knotted Fan Coral Acabaria splendens is known by a number of common names including as the Pacific Sea Fan, Knotted Fan Coral, and Red Gorgonian, as well as the Acabaria Fan Coral and Acabaria Sea Fan. It is an attractive beauty that can be a violet red, or red to orange color, with white or light yellow polyps. Like all members of its family, Melithaeidae, the Acabaria genus is characterized by contrasting disks or knobs between the branches called "internodes". These knobs are composed of sclerites like those found in other soft corals, as well as a protein substance called gorgonin which allows for more movement, some flex in the gorgonian.

   The Acabaria genus is notoriously difficult to keep alive in captivity. They are aposymbiotic which means they do not carry zooxanthellae, so they must be fed regularly. They need a constant supply of planktonic foods, which can foul the water quickly. They are easily overgrown by algae, so a dim area of the tank is needed to keep them healthy. These corals are best kept by highly advanced aquarists who have had success with other gorgonians and are willing to devote the time and resources needed for its survival.

To learn more about these fascinating Octocorals see:
What Are Gorgonians?
Types of Gorgonians, Sea Fans and Sea Whips


  • Kingdom: Animalia
  • Phylum: Cnidaria
  • Class: Anthozoa
  • Order: Alcyonacea
  • Family: Melithaeidae
  • Genus: Acabaria
  • Species: splendens
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Scientific name    Suborder: Scleraxonia
   Family: Melithaeidae
   Species: Acabaria splendens

Distribution / Background    Gorgonian Information: The Acabaria genus was described by Gray in 1870. There are over 46 species. Some common names these corals are known for are Gorgonian Sea Fan or just Sea Fan. It is unknown if the Acabaria genus has been propagated in captivity.

   The Splendid Knotted Fan Coral A. splendens was described by Thomson & McQueen in 1908. Some common names they are known for are Pacific Sea Fan, Knotted Fan Coral, Red Gorgonian, Acabaria Fan Coral, and Acabaria Sea Fan.

   Where Acabaria Corals Are Found: The Acabaria genus are found in the Red Sea, Indo-Pacific, Indian Ocean, and the Maldives.

   Acabaria Coral Habitat: The Acabaria genus habitat includes reef crests, current swept slopes, and calm open water where they live along shaded areas or under overhangs and in dimly lit caves.

Status    The Acabaria genus is not on the IUCN Red List for Endangered Species.

Description    What do Acabaria Corals look like: The Acabaria genus can come in red, yellow, and orange with white or light yellow polyps. The Acabaria genus has a dichotomous structure which is a random "Y" shaped branch pattern with little disk type knobs between the branches. The axial skeleton of Gorgonians in the suborder Scleraxonia are calcium based like other Octocorals. They have sclerites that are fused, or mostly fused, in their axis, their rind, and sometimes in their polyps.

   The Splendid Knotted Fan Coral A. splendens can be a violet red, red to orange color with white or light yellow polyps. Like all members of its family, Melithaeidae, the Acabaria genus is characterized by contrasting disks or knobs between the branches called "internodes". These knobs are composed of sclerites like those found in other soft corals, as well as a protein substance called gorgonin which allows for more movement, some flex in the gorgonian.

   Classification of gorgonians in general is done by some simple visual clues such as colony size, shape, axis structure, color, polyp placement, and pattern of branches. Getting a little more technical, they also look to see if the polyp is autozooid or siphonozooid. Then there is the more exacting use of chemotaxonomy. This is being used to show the different terpenoids or other chemicals produced by each gorgonian species

Difficulty of Care    Gorgonian Care: The Splendid Knotted Fan Coral A. splendens is difficult to care for due to their dietary needs. They also need a low light level and enough water flow to avoid having algae grow on them.

Foods / Feeding    Gorgonian Feeding: In the wild, Acabaria corals have developed several feeding strategies. They capture microscopic food particles from the water column and can absorb dissolved organic matter. They are aposymbiotic which means they do not carry zooxanthellae.

   In captivity, the Splendid Knotted Fan Coral needs plankton type foods daily.

Aquarium Care    Stable tank conditions are needed to keep the Acabaria genus. Doing water changes of 20% a month or 10% biweekly is needed, although it is suggested that doing 5% water changes once a week will replenish many of the needed additives. Iodine, calcium, strontium, and other trace elements can be added to maintain proper levels for good growth.

   Suggested levels for Acabaria species are:

  • Calcium:  400 - 450 ppm
  • Alkalinity:  3.2 - 4.8 MEQ/L (8 to 11 dKh - 10 is recommended)
  • Phosphates:  0, zero.
  • Magnesium:  1200 - 1350 ppm. (Magnesium makes calcium available, so if your calcium is low, check your magnesium levels before adding any more calcium.)
  • Strontium:  8 - 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 the Splendid Knotted Fan Coral, along with some fish for organic matter production. A mature tank (well over a year old) is advised to increase the successful keeping of Acabaria.

   Provide proper lighting and water movement, and they must be anchored down. A moderate and turbulent water flow and a dim light source are needed for the Splendid Knotted Fan Coral to do well. These Octocorals are very peaceful but may be at risk of being overgrown by other gorgonians, so adequate space should be provided between the different species.

  • Minimum Tank Size / Length: 50 gallon (190 L) or larger
  • Marine Lighting: Low, dim
  • Temperature: 72° - 73° F (20° - 28° C)
  • Salinity / Specific Gravity: 1.023 - 1.025
  • Water Movement: Moderate and turbid
  • Water Region: Bottom of the aquarium

Compatibility and Social Behaviors    The Splendid Knotted Fan Coral and other Acabaria corals are very peaceful and pose no threat to any other corals or gorgonians. Other gorgonians may over take the peaceful Acabaria corals, so they will need to be kept at a distance. They get along with their own genus.

   Butterflyfish feed on gorgonian polyps or tissue. Butterfly fish will constantly chow, so they are not the best idea for a tank mate. Some angelfish will also pick at the polyps, but can be housed with them if the angelfish is well fed.

Sex - Sexual differences    No sexual difference in appearance is known.

Breeding and Reproduction   The Acabaria genus may reproduce by by breakage, fragmentation. and they may also spawn like other gorgonians for sexual reproduction.

  Propagation of gorgonians consists of using severing or clean cuts. Tearing the coral will result in infection. Be cautious with the use of glues, as many gorgonians react badly to the chemicals. However an underwater epoxy has been suggested by some. Containment is recommended if the frag survives. This involves keeping the frag in one spot, say a small piece of upright pvc, around the same height as the frag, with sand or rubble at the bottom. This will keep the frag from blowing over before it can take root. It is suggested to drill holes in the pvc to keep the water flowing.

Potential Problems   The Acabaria genus is susceptible to algae and cyanobacteria accumulating on its branches. This problem can lead to red band and black band infections. Keeping water flow strong will help prevent this. If your gorgonian does get this, you can at times cut off the bad part and hope the rest will recover.

Availability    Gorgonians for Sale: The Splendid Knotted Fan Coral A. splendens is very rare in the aquarium hobby, and not readily availabe at pet shops and on line.

References

Author: Clarice Brough CRS, Carrie McBirney

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