Animal-World > Aquarium Coral Reefs > Stony Corals SPS > Boulder Coral - Porites sp

Boulder Coral

Christmas Tree Worm Rock, Encrusting Boulder Coral

Boulder Coral, Porites sp., also known as Encrusting Boulder Coral, Christmas Tree Worm Rock, and Porites CoralPorites Porites sp.Photo © Animal-World: Courtesy David Brough

   The slow growing Boulder Coral can live a very long time in nature, with some being close to 1000 years old!

   The Porites genus are some of the longest lived species on earth, and can attain massive proportions in the wild. They also form some of the largest coral colonies, with growths reaching about 26 feet (8 m) in height. Based on their rate of growth, it is estimated that some of these large colonies can be close to 1000 years old. However this is not a problem for the reef aquarium because they are very slow growing corals, averaging only 1/3 of an inch (9 mm) a year.

   Encrusting species of Porites, like the Boulder Coral, often enter the aquarium trade on live rock, or as a Christmas Tree Worm Rock. They come in many attractive colors including green, blue, golden yellow, yellow, purple, and pink. These colors can be very vivid, and for many specimens the color will be brought out under high intensity lighting.

   Those Boulder Corals called the Christmas Tree Rock are embedded with colorful Christmas Tree Worms or Fan Worms that bore into their skeletons. Their commensal relationship with these worms are one of many "partnerships" we see in marine life and it is truly another marvel of the ocean. Though they are sold for the 'worm', they should be cared for as the coral, because the worms will not live if the coral dies.

   The Boulder Coral Porites sp. can be difficult to care for initially, but once it is acclimated can be very hardy. The species that come connected to your live rock tend to be the hardy species whose tentacles are out day and night. Harder to care for species will have tentacles out at night only, or during the day only. The Boulder Coral is best kept in a shallow display with high light and fast water movement. The Porites genus has been propagated in captivity, and some beautiful captive grown specimens are available.


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Scientific name    Family: Poritidae
   Species: Porites sp.

Distribution / Background    Porites Coral Information: The Porites genus was described by Link in 1807. There are approximately 122 nominal species, but it is still unknown how many of these are true species. In Australian waters, all 16 species that are found there are considered true species. They have proven difficult to classify as individual species because of their minute calices. Some common names these corals are know for are Finger Coral, Jeweled Coral, Christmas Tree Worm Rock, Boulder Coral, Plating Jewel Coral, Jeweled Finger Coral, and Porites Coral. Some of the captive grown Porites have aquacultured names like Canary porites Coral P. cylindrica, Limited Edition Mike Paletta's Purple Porites, and Amethyst Porites P. annae.

   In some areas, Porites nigrescens, are accidentally imported with the blue sponge, Haliclona sp., which is found in Indonesia. Oddly in the ocean, the sponge usually kills P. nigrescens, but due to the sponge's mortality rate, it usually dies in captivity/transport, leaving the "victim" or Porites intact. If you do get these 2 specimens together, separating them is needed to insure the Porites corals survival. This species of Porites is actually very hardy in captivity.

   Where Porites Corals Are Found: The Porites genus are found in most of the tropical oceans and seas of the world.

   Porites Coral Habitat: Porites genus are found in a wide range of habitats. They inhabit most reef environments, from lagoons to reef fronts as well as at the base of coral mounts and in sandy substrates that can be sloping or flat. The water is usually very turbid with a high current. Some species have also been found surviving in lower salinity.

Status   Many of the Porites genus are on the IUCN Red List of Endangered Species. Most species are listed as Data Deficient (DD), Least Concern (LC), Vulnerable (V), and Near Threatened (NT), but about three are listed as Endangered (E) and one as Critically Endangered (CR).

Description    What do Porites Corals look like: The skeletons of the Porites genus are lightweight and porous. They have multiple growth forms that can grow quite large in size. Growth forms include flat colonies that are encrusting, flat leaf-like sheets, massive colonies that are dome shaped when large, and branching colonies. Some species can have several of these characteristics in one colony, because their growth formations are affected by water flow.

   The Encrusting Boulder Coral can grow in massive spherical or hemispherical shapes. These colonies can reach 26 feet (8m) in height and can be over 16 feet (5 m) in diameter. They are very slow at expanding, only growing 1/3 of an inch (9 mm) a year. There are colonies in the ocean that are estimated at over 1000 years old.

   The Porites genus corallites are small, submerged, and filled with septa. The number of septa the Porites genus have give the corals a jeweled appearance, as if jewels were embedded across the surface. They are often confused with the Montipora corals as they both have corallites that are extremely small. However Porites have many differences in growth form, and their corallites are usually larger and more compact than those of the Montipora corals. The Montipora corals also lack the same type of septa.

   The colors of Porites sp. can be green, blue, mustard, yellow, purple, pink, as well as muted versions of these colors. They will often shed a mucous layer every month during the full moon to rid themselves of waste.

Difficulty of Care    Porites Coral Care: The Boulder Coral Porites sp. can be difficult to care for, but once it is acclimated can be very hardy. The species that come connected to your live rock tend to be the hardy species whose tentacles are out day and night while the harder to care for species can have tentacles out at night only, or during the day only.

   Porites often shed their outer surface layer to rid themselves of wastes and algae. It is actually done around the same time as the full moon. This waste may be removed to avoid fouling the water in smaller systems.

Foods / Feeding    Porites Coral Feeding: In the wild, small polyp stony (SPS) 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. The small tentacles of the Porites species however, make capturing planktonic foods less viable than other SPS.

   In captivity, they do best in well-feed reef tanks. Small polyp stony (SPS) corals gets much of their nutrition from the zooxanthellae that lives in their tissues, and organic matter in the water. The Porites corals are generally supported by high lighting and small organics release into the water column, but may benefit from liquid coral foods or planktonic liquid preparations.

Aquarium Care   Pristine tank conditions are typically needed to keep all SPS corals. Keep the nitrate levels low, and maintaining calcium and alkalinity levels. Typically you can do water changes of 20% a month, 10% biweekly or 5% weekly. It has been noted that 5% weekly water changes replenish many of the needed additives. With higher concentrations of coral with calcareous skeletons, there may be a need put in additional additives to maintain proper levels for good growth.

   Suggested levels for Porites species are:

  • Calcium:  400 to 450 ppm (closer to 450). If the coral does not have enough calcium, it will not grow.
  • Alkalinity:  3.2 TO 4.8 MEQ/L (8 to 11 dKh - 10 is recommended)
  • Phosphates:  0, zero. Phosphates are the worst of all and all corals hate them.
  • Magnesium:  12000-1350. 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 your Boulder 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

   Like other Porites, the Boulder Coral is best kept in a shallow display with high light and fast water movement. House them with fish and stir up the substrate to release organics into the water column. Make sure that no other corals can come in contact with your Porites. This Boulder Coral is not aggressive, position it with plenty of room between it and other corals.

  • Minimum Tank Size / Length: 20 gallons (75 L) or larger
  • Marine Lighting: High
  • Temperature: 72° - 80° F (22° - 27° C)
  • Salinity / Specific Gravity: 1.023 - 1.025
  • Water Movement: Very strong and turbulent
  • Water Region: Top of the aquarium

Compatibility and Social Behaviors   Porites are not aggressive and plenty of space should be given between them and other corals. These are perhaps some of the most submissive corals, but they are also very adaptable. They can often survive attacks from other corals, growing and re-calcifying even if portions of their skeleton are dead.

Sex - Sexual differences    Colonies are either male or female, yet there are no visible differences to the outward appearance.

Breeding and Reproduction   The small polyp stony (SPS) corals are male and female and can reproduce both sexually and asexually. In the wild, for most of the Portites genus, sexual reproduction is done internally. These corals have male and female colonies, a trait they share with the Goniopora genus. The Porites genus male colonies release free-swimming sperm that the female colonies absorb. The female polyps brood the planulae in the body cavity rather than releasing eggs into the water column. They release the mature larvae when their development has been completed. They must rely on free swimming sperm released from the male colony to reach them. Some female species will release egg bundles into the water to meet up with sperm from male colonies, but there only a few that reproduce this way. In the wild small polyp stony (SPS) corals also spread asexually, from breakage due to storms and fragmentation.

   Propagating Porites corals is done by breaking the coral. Leverage the coral against a hard surface, then use a chisel, plastic pliers, hard table edge, or some even drop it on the floor to obtain frags. For some species you may want to glue the frag to a plug or rock, using the 2-part epoxy or underwater putties. Gloves are suggested. Give the frag ample water flow. They do not grow quickly.

Potential Problems    The Porites spp. are hard corals that once established, may not be susceptible to many diseases. But they can still get the same illnesses that any other small polyp stony (SPS) coral can get under poor conditions, or when they first arrive. There are several ailments these corals are subject to including bleaching, black-band disease, white-band disease, algae encroachment, and others. Here are some of the ailments and suggested treatments:

  • Black-band disease: To prevent necrosis, and fight black band disease, the corals can be treated with Tetracycline at 10 mg per quart/liter according to one author.
  • Bleaching: This is the mass expulsion of zooxanthellae. Stress can trigger it and it generally will take the aquarist by surprise. The coral is still alive with slightly pigmented tissue. (will not be pure white) A suggestion is to turn down your lights so the zooxanthellae does not spin out of control and right out of your coral. Otherwise, once bleaching occurs, it has a 50/50 chance of complete healing. They will be prone to illness at this time.
  • Parasitic Animals: There is a Nudibranch, Phestilla lugubris that will feed on your Porites genus. Symptoms are patches of discolored polyps or tentacles not extended.

   if your stony coral has any kind of tissue recession, you may be able to remove the unhealthy part. Just make sure you cut into some of the healthy part also, to be sure there is no disease encroaching on the healthy tissue. Also, keep out the cyanobacteria and algae with good water movement, and your coral will stay happy.

Availability    Porites Corals for Sale: The Boulder Coral Porites sp. is moderately easy to find at pet shops and on line. Online they can run about $40.00 to $60.00 USD or more depending on size and/or color.

References

Author: Carrie McBirney; Clarice Brough, CRS

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