Black Sun Coral

Branching Black Sun Coral, Black Tube Coral
Black Cup Coral, Black Tubastrea, Green Sun Coral

Black Sun Coral, Tubastraea micranthus, also known as the Branching Black Sun Coral, Black Tube Coral, Black Tubastrea, and Green Sun CoralTubastrea micranthaPhoto © Animal-World: Courtesy Greg Rothschild

   The Black Sun Coral is very intriguing, first in name and then with its gorgeous appearance!

   The color and growth form of the fascinating Black Sun Coral Tubastraea micranthus will peak the interest of all coral enthusiasts. They are also known as the Branching Black Sun Coral, because they form erect colonies that are richly branched and tree-like. In the wild, these colonies can reach 40" (1 m) in height. At this time, they are the only discovered branching version of this genus.

   The Black Sun Coral has very fleshy polyps with its corallites, the hard round, tubular structure the polyps live in, situated on the branches. The corallites are covered with a tissue, called the coenosteum. Their polyps tentacles can be a greenish black to brownish black with the very center of the polyps and the coenosteum and being olive green to brownish black. The colors can be variable, but the polyps are not the dark brown or black that can be found on the coenosteum.

   The polyps of the Black Sun Corals extend mostly during evening hours, though they can be coaxed out during the day if food is present. During the day, the coral is completely withdrawn and only the dark coenosteum is visible, making it look like a tree with raised round flat nubs all over the branches. Other common names these corals are know for are Black Tube Coral, Branching Black Sun Coral, Black Cup Coral, Black Tubastrea, and Green Sun Coral.

   Although the other species in the Tubastraea genus are referred to as non-reef building corals, or ahermatypic, T. micranthus is actually considered hermatypic or reef building. This is due to the fact that their skeleton is not only denser than the rest of the species in this genus, but denser than most corals on the reef.

   The T. micranthus are some of the most durable corals in the ocean, resisting damage by the strong forces of nature, like hurricanes and cyclones. Their surprising strength was also noted when, even after nuclear blasts, the T. micranthus was one of only a few corals that were not fully demolished and still adhering to the reef. Despite its hardiness in the wild, the Black Sun Coral is a delicate coral to handle. Its fragile branches will break easily, so It must be moved carefully by picking it up from its underside.

   The Black Sun Coral is moderately difficult to care for and labor intensive. It needs several daily feedings, good filtration, a very strong water movement, and regular substantial water changes. In the average aquarium it is near impossible to provide the extreme water movement and extreme amount of food needed for its captive survival. It is only recommended for the advanced aquarist. Its success depends on a very dedicated aquarist who can provide the right environment and the on-going care of this beautiful coral.

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Scientific name    Family: Dendrophylliidae
   Species: Tubastraea micranthus (T. micrantha)

Distribution / Background    Tubastraea Coral Information: The Tubastraea genus was described by Lesson in 1829. These corals are referred to as azooxanthellate or non-photosynthetic corals, which means they only survive with foods, and lighting has no affect on their growth. They are also mostly non-reef building corals, or ahermatypic, with the exception of T. micranthus that has a much denser skeleton.

   There are 7 Tubastraea species. They are the Yellow Sun Coral or Golden Cup Coral T. aurea, Orange Cup Coral T. coccinea, Brown Cup Coral T. diaphana, Orange Sun Coral T. faulkneri, Floreana coral T. floreana, Black Sun Coral or Green Sun Coral T. micranthus (previously known as Dendrophyllia migrescens), and T. tagusensis. Some common names the Tubastraea species are known for are Orange Cup Coral, Brown Cup Coral, Pink Cup Coral, Rose Coral, Orange Polyp Coral, Black Tube Coral, Sun Coral, Black Sun Coral, Golden Cup Coral, Sun Flower Coral, Tube Coral, Green Cup Coral, and Black Branching Sun Coral.

   The Black Sun Coral Tubastraea micranthus was described by Ehrenberg in 1834. T. micranthus, rather than micrantha, is the spelling that is recognized by ITIS, the Integrated Taxonomic Information System. Some other common names these corals are know for are Black Tube Coral, Branching Black Sun Coral, Black Cup Coral, Black Tubastrea, and Green Sun Coral.

   Where Tubastraea Corals Are Found: The T. micranthus are found in the Indo-Pacific and the Red Sea.

   Tubastraea Coral Habitat: The T. micranthus are the deepest dwellers of this genus, being found at 160 feet (50 m). They are found on fore reef surf zones along with other hermatypic corals and reef fauna, in extremely strong waters which flow at a rate of 3 feet per second (1 m per second). This strong laminar flowing water provides the Branching Black Sun Coral with a rich supply of zooplankton at an amount that is near impossible to duplicate in captivity.

Status    The T. micranthus is not on the IUCN Red List of Endangered Species.

Description    What do Tubastraea Corals look like: The T. micranthus form branching colonies that can reach 40" (1 m) in height. Their Corallites, or the hard round, tubular structure the polyp lives in, are situated on the branches. The corallites are covered with a tissue, called the coenosteum.

   The polyps of the Black Sun Coral are very fleshy, and extend mostly during evening hours, though they can be coaxed out during the day if food is present. Its tentacles are greenish black to brownish black with the coenosteum being olive green to brownish black, and the very center of the polyps being the same color as the coenosteum. During the day the coral is completely withdrawn and only the dark coenosteum is visible, making it look like a tree with raised round flat nubs all over the branches. It is said these corals only grow 1.6" a year (4 cm). Life span is unknown.

Difficulty of Care    Tubastraea Coral Care: In generally, the Tubastraea genus can be easy to moderate to care, for depending on the dedication of the aquarist. However the Black Sun Coral is moderately difficult to care for, as iIt is near impossible to provide the extreme water movement and extreme amount of food needed for its captive survival. It is best left to advanced, expert aquarists. An alternative dark version of this genus is the non-branching Brown Cup Coral T. diaphana, which is a dark brown color, which is easier to care for.

Foods / Feeding    Tubastraea Coral Feeding: The Tubastraea genus are referred to as azooxanthellate, or non-photosynthetic corals. This means that, unlike most other large polyp stony (LPS) corals, they do not have a symbiotic relationship with the marine algae zooxanthellae. To feed they capture planktonic organisms, food particles from the water column, and can absorb dissolved organic matter. Some also eat small fish.

   In captivity, the Black Sun Coral needs to be fed twice to 3 times daily. Feed decent sized foods like enriched live or defrosted, or freeze dried adult brine shrimp, mysis shrimp, and other similar sized prey. Soak the food in a vitamin supplement. If they are well fed, they get a "bloated" look.

   New colonies may need the juice of the shrimp wafting across the tops of their closed polyps for a few nights before they start to feed. Be patient and persistent since this can take up to 2 weeks. Feeding the same time each evening will get the best response. These corals will stop extending their tentacles and gradually waste away if they are not fed.

   There are several ways to approach feeding your Tubastraea, so they can hold onto the food.

  • One way is to take the coral out of the tank into a container with warm tank water (or float the container in the tank to keep it warm) and feed the polyps a high concentration of food. After the coral has fed, it can be put back into the tank, and the fouled container of water discarded. This option will help keep the water quality high. Remember to wiggle the coral so the polyps pull in before removing.
  • The second way is to leave the coral in the tank. Put on a feeding "cap" to keep the food from blowing away, and also to keep shrimp and fish from taking the food out of the polyp's mouth.
  • The third choice is to simply turn off the pumps. But remember to turn them back on after they have fed.

Aquarium Care    Typical water changes of 20% a month, 10% biweekly, or 5% weekly are needed. It has been noted that 5% weekly water changes replenish many of the needed additives. Frequent water changes help to supply trace elements, but with higher concentrations of coral with calcareous skeletons, there may be a need put in additional additives to maintain proper levels for good growth. Trace minerals and iodine may be added

   The following water supplements are suggested for Tubastraea species:

  • Calcium:  380 to 430 ppm. If a large poly stony (LPS) coral does not have enough calcium, it will not grow. (Seachem makes a calcium additive that states 385 as sufficient)
  • Alkalinity: 3.5 MEQ/L (8 to 12 dKh, 10 is recommended)
  • Phosphates:  0, zero. Phosphates are the worst of all and all corals hate them.
  • Magnesium:  1200 - 1350 minimum. Magnesium makes calcium available, so if your calcium is low, check your magnesium levels before adding any more calcium.
  • Strontium:  8 - 10

Aquarium Parameters   A well-feed live rock/reef environment is what is needed for the Black Sun Coral, along with some fish for organic matter production. A mature tank is recommended.

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

   They need to have a very strong water movement, yet are tolerant of lighting in the aquarium. A strong skimmer is recommended to take care of the nutrient load added by the heavy feedings needed for these corals.This is a peaceful species, but other corals may not be, so provide adequate space between species.

  • Minimum Tank Size / Length: 50 gallons (190 L) or larger
  • Marine Lighting: Any
  • Temperature: 74° - 83° F (23° - 28° C)
  • Salinity / Specific Gravity: 1.023 - 1.025
  • Water Movement: Strong
  • Water Region: All areas of the aquarium, where it's easy to feed

Compatibility and Social Behaviors   The T. micranthus is peaceful towards other corals. However they do not have strong stinging tentacles, so need to be kept away from other corals. The only impact they will have on other corals is connected to their need to be fed large amounts of food, that may foul the water.

   The Tubastraea genus is preyed upon by the Tubastrea Snail Epitonium billeeanum. These snails have a very similar color and shape as the coral's polyps when closed. The nudibranch Phestilla melanobrachia is another pest. It comes in the color of the specific Tubastraea that it feeds on. Check your specimen closely when you get it, to find and remove these pests.

Sex - Sexual differences    Differences are unknown

Breeding and Reproduction   The large polyp stony (LPS) corals are hermaphrodites, male and female within the same organism, 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. The Tubastraea genus can reproduce asexually as well through budding.

   In captivity, propagating the Tubastraea genus can be done by breaking off pieces from a healthy colony. Another way is to keep the coral well fed with good water flow, and let it propagate by itself.

Potential Problems   Light will not harm the Tubastraea species, but they do not have a very good defense against algae. Algae grows fast in lit areas, and if algae is allowed to grow on the T. micranthus, it will die eventually. Strong water movement is a must. Putting the coral in areas under ledges that usually do not have the water flow they need, can also cause algae growth.

   The Tubastraea species have voracious appetites and must be fed regularly. These corals will stop extending their tentacles and gradually waste away if they are not fed.

Availability    Tubastraea Corals for Sale: The T. micranthus is easy to find at pet shops and on line. Online they can run about $36.00 USD or more depending on size and/or color.

References

Author: Carrie McBirney, Clarice Brough CRS
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