Fire Coral

Stinging Coral, Box Coral, Bladed Fire Coral, Wello Fire Coral

Picture of a Fire Coral, Millepora alcicornis, hydrocoralBranching Fire CoralMillepora alcicornisPhoto © Animal-World: Courtesy David Brough

   The Fire Coral is also known as a "stinging corals" because if touched it will produce a burning or stinging sensation!

   The Fire Coral Millepora alcicornis belongs to the class Hydrazoa, and are known as hydrocorals. This species is just one of the many members in the Millepora genus. This genus is the common "fire coral" or "stinging coral" which causes a burning sensation if touched. These Hydrocorals have a potent sting. It is usually just a mild sting, but for some it can be all the way up to anaphylactic shock. Divers, snorkelers, and aquarists need to wear gloves when handling or anywhere near the coral.

   Fire Corals could be described as very hardy "soft" corals, only with a similar appearance and habitat as the stony corals. But the Millepora genus is not considered a stony coral due to its internal structure. They do produce a hard aragonite skeleton and aid in reef building, yet inside are canals that house all of the polyps and aid in food distribution. This makes them no where near as dense and hard as a stony coral.

   The Millepora genus can take many forms including arborescent (treelike), plate-like, encrusting, lace-like, box-like or columnar. These different forms develop in conjunction with the water flow where they are found. Encrusting colonies are the initial growth form of these hydrocorals. In areas of strong water flow they will continue to encrust. But in a low water flow area they will develop into a lacy branching form (similar to the Stylaster Lace Corals, but not on a single plane). These can become leaf like or blade like, even a box like shape, where water flow increases in strength. Thus the common names they are known for besides Fire Coral and Stinging Coral are Branching Fire Coral, Box Coral, Bladed Fire Coral, Finger Coral, Ginger Coral, and Wello Fire Coral.

   Don't be dissuaded from keeping Fire Corals because of their sting, since they are hardy and easy to propagate, just be careful and wear gloves. In the wild, they are adaptable to many environments, thus contributing to their hardy nature. They let you know their light needs by their color, with yellow being perfect and brown being "not enough". They also need strong water movement, or they will not grow as much.

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Scientific name    Family: Milleporidae
   Species: Millepora alcicornis

Distribution / Background    Millepora Information: The Millepora genus was described by Linnaeus in 1758. This is the only genus in the Milleporidae family. There are at least 48 species, with a few being M. alcicornis, M. complanata, M. dichotoma, M. exaesa, M. murrayi, M. nitida, M. platyphylla, M. squarrosa, M tenella, and M. tenera. Some common names these hydrocorals are known for are Bladed Fire Coral, Wello Fire Coral, Fire Coral, Box Coral, Firecoral, Stinging Coral, Finger Coral, Ginger Coral, and Wello Fire Coral. The Millepora genus has been propagated in captivity, yet is not always available.

   Where Millepora Are Found: The Millepora genus are found from the Red Sea, south to Madagascar, then east toward Australia's west coast in the Houtman Abrolhos Island area. They are also found from the Great Barrier Reef all the way around Australia's north coast and mid way down the east coast, then from New Caledonia all the way to the Tuamotu islands, then north to the Hawaiian Islands, circling back to the Southern tip of Japan, then westward including all of Indonesia and back to the Red Sea. Some are found in the Atlantic Oceans including the Gulf of Mexico and up to Canada via North America's east coast.

   Millepora Habitat: The Millepora genus are found at depths from 0 - 130 feet (40 m) . They inhabit areas of high current and light, including reef slopes and projected parts of the reef that have strong wave and current action.

   The Millepora genus is commonly one of the first corals on the scene of a new reef and the last ones to leave when a reef is dying. They cover 10% to 50% of reefs, as well as being a small part of all reef building corals.

Status    The following species from the Millepora genus are currently on the IUCN Red List for Endangered Species:

  • Millepora alcicornis: Least Concern (LC)
  • Millepora boschmai: Critically Endangered (CE)
  • Millepora braziliensis: Data Deficient (DD)
  • Millepora complanata: Least Concern (LC)
  • Millepora dichotoma: Least Concern (LC)
  • Millepora exaesa: Least Concern (LC)
  • Millepora foveolata: Vulnerable (VU)
  • Millepora intricata: Least Concern (LC)
  • Millepora latifolia: Vulnerable (VU)
  • Millepora murrayi: Vulnerable (VU)
  • Millepora nitida: Data Deficient (DD)
  • Millepora platyphylla: Least Concern (LC)
  • Millepora squarrosa: Least Concern (LC)
  • Millepora striata: Endangered (EN)
  • Millepora tenera: Least Concern (LC)
  • Millepora tuberosa: Endangered (EN)

Description    What do Millepora look like: The Millepora genus grows in many formations, all dependent on water movement. They can form branching, laminar, encrusting and massive colonies. This genus is not considered a stony coral due to its internal structure. They do produce a hard argonite skeleton, yet inside are canals that house all of the polyps and aid in food distribution. This makes them no where near as dense and hard as a stony coral. The smooth surface is densely dotted with mouths that look like small pores. The colors of the Millepora spp. are usually a mustard yellow to dark brown and cream with white or lighter colored tips, with some rarer species being green or pink.

Encrusting Fire Coral, Millepora Sp., Box Fire CoralEncrusting Fire CoralMillepora Sp.Photo © Animal-World: Courtesy John Rice

At first glance this doesn't look anything like
a typical fire coral. Most are highly branched
like small bushes. As it turns out though,
there is an encrusting type of fire coral
and this is it!

   On the smooth surface, the dense populations of pores are called called gastropores and they contain polyps in two sizes. The larger polyps are called gastrozooid polyps. They tend to stay within the corallum, (not extending outward past the surface of the coral), and help to digest food and pass it through the colony within the skeletal structure. The smaller polyps surrounding this gastrozooid polyp are called dactylozooids, and they number between 5 to 7. The dactylozooids look like tiny hairs that stick up beyond the surface, giving these hydrocorals a fuzzy appearance.

   The dactylozooids polyps have a strong toxin to sting prey. Once stung, these polyps will then bring the food inward to the gastrozooid polyp in the middle, which will engulf the prey and digest it. These corals will burn your skin if you are not careful. They are a bane to divers and it is best to look and not touch in the wild.

   Millepora Life Cycles: The Fire Corals Millepora spp. can grow up to 12" (30 cm) in height. Encrusting forms can sense nearby corals and will grow towards them and then encrust over them, using their structure as a base.

   Some of the better known species:

  • M. alcicornis
    The Branching Fire Coral is found in several areas that do not have strong wave action, and so are generally the branching form. This coral will typically overgrow and take the shape of any coral it gets near, especially gorgonians.
  • M. squarrosa
    The Box Fire Coral is from the Atlantic and are usually pink to cream with white or lighter colored tips. They tend to grow in a box-like formation from an encrusting base.
  • M. complanata
    The Blade Fire Coral is found in the Caribbean and grows in a blade formation.
  • M. complanata, M. dichotoma, and M. platyphylla
    These hydrocorals are found in surge areas with strong waves and generally form heavier leaf-like, fanlike or vertical plate-like structures.
  • M. tenella and M. exaesa
    These are found throughout the reef zones and form lumpy protrusions or very heavy, thick branches

Difficulty of Care    Millepora Care: The Fire Corals can be easy to care for as long as lighting and water flow are strong. They will turn brown under inadequate lighting. They adjust themselves to the water flow in your tank as they grow, so once established try not to move them if you can. They will cease to grow very much at it there is weak water movement.

   Millepora care in the aquarium requires that you be very careful. These hydrocorals have a potent sting. It can just be a mild sting for some, but can be all the way up to anaphylactic shock for others. Needless to say, wear gloves when you are handling or anywhere near the coral. Don't be dissuaded from keeping them because of their sting, since they are hardy and easy to propagate, just be careful and wear gloves.

   Keeping powdered meat tenderizer around is a good idea if you own, or will be purchasing one of these corals. Ammonia and warm water are two other suggestions, but meat tenderizer seems to be a constant as a relief cure. This will alleviate the burn and itch of their sting. These items are a neutralizer for these particular forms of nematocyst stings, and will not necessarily work for jellyfish stings or other types of nematocyst stings.

Foods / Feeding    Millepora Feeding: Fire Corals depend on light and photosynthesis for about 75% of their growth, they also do well being fed plankton These "hungry hydrocorals" will also eat live brine shrimp or any defrosted foods like mysis, etc. that get into their "hairy" stingers. Turning the pumps off while they feed is a good idea.

Aquarium Care    Stable tank conditions are required to keep the Millepora genus. Do typical 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.. Although similar to a "soft coral", they do have calcareous skeletons and need parameters similar to hard corals. Additions of iodine are also recommended.

   Suggested levels for Millepora species are:

  • Calcium:  400 to 450 ppm (Seachem makes a calcium additive that states 385 as sufficient for corals)
  • Alkalinity:  3.2 TO 4.8 MEQ/L (8 to 11 dKh - 10 is recommended)
  • Phosphates:  0, zero.
  • Magnesium:  1200 - 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

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 reef environment is what is needed for your Fire Coral. A mature tank (well over a year old) is advised to increase the chance of successfully keeping Millepora.

  • Minimum Tank Size / Length: Nano 1 gallon (3.8 L) or larger
  • Marine Lighting: High (not necessarily Metal Halide)
  • Temperature: 72° - 78° F (22.2° - 25.5° C)
  • Salinity / Specific Gravity: 1.023 to 1.025
  • Water Movement: Strong. Surge and turbulent flow.
  • Water Region: Bottom of the aquarium if using Metal Halides, middle for other lighting.

Compatibility and Social Behaviors    The Millepora genus is very aggressive. These hydrocorals will encrust and take over other corals, so keep your eye on their growth rate. Make sure you space them at least 6" from other corals. Possibly place them on a rock in the sand away from the main rock work to keep them from encrusting on to the main rock formation.

   Fire Corals willl actually grow faster in the direction of other corals at a whopping 1" or more a month. They are especially fond of gorgonians from the Plexaura genus. They can actually sense a gorgonian, overtake it, and assume its shape. Ironically, a strong, swift water current can snap this structure in half since the gorgonian is now dead and brittle underneath.

   Hawkfish are often found on these corals, and use them for protection. They can do this because their tissue-less pectoral fins are immune to the sting.

Sex - Sexual differences   Fire Corals primarily consist of hydroid colonies. These usually have separate sexes consisting of either male or female members. Thus each colony can produce only one type of gamete, either eggs or sperm. There is not usually both sexes in the same colony.

Breeding and Reproduction    Millepora hydrocorals have two principle forms; the predominant body type is the polyp and the other is bell-shaped or the shape of a thin disk. Their life cycle originates as a sessile polyp, and in this stage it multiplies asexually. Animals in the polyp stage are known as "hydroids". The polyp stage can then bud, forming a free-swimming, planktonic animal, like the jellyfish. In this stage they are known as "medusa" and can produce eggs or sperm.

   The gamates of Fire Corals are sexually mature in about 20 -30 days, much sooner than the months it can take for stony corals. In the wild, the Millepora genus is not dependent on lunar cycles and will release free swimming medusae at the same time as other fire corals. Their medusae do not live for very long, only a few hours.

   Propagation is rather simple for Millepora corals. Breaking and cementing the pieces onto plugs or rock is a typical way to frag this coral. Rubber banding to a plug or rock is another way that has been used. However, there is another way that is quite ingenious. Place rubble rock around the Millepora, and let their encrusting tendency take over and cover the rubble. Then simply break away a piece of rubble as a frag.

Potential Problems    The Millepora genus, although not susceptible to many things, does have few areas that can lead to its demise. Having zooxanthellae algae makes them susceptible to bleaching. Higher temperatures than they are used to will cause this too, along with their being too close to a Metal Halide lamp.

   Predators are another nuisance. These include the Pyrgomatina barnacles, both commensal and carnivorous marine worms, (polychaete), and Filefish from the Aluterus and Cantherhines genus. The Crown of Thorns Starfish Acanthaster planci, will also eat these hydracorals, even thought they are stung in the process.

   Some of the most interesting predators are nudibranchs, such as the Phyllidia nudibranchs. These feed on Fire corals but can ingest the stinging nematocysts without digesting them. They then use these same nematocysts as defense by transporting them through their intestines to their dorsal appendages. When the sea slug feels threatened, it will then fire the stinging nematocysts at the predator!

Availability    Millepora Hydrocorals for Sale: The Millepora genus is very hard to find at pet shops and on line. These corals can sometimes be sold under "Hydrocorals" or "Fire Corals". They may possibly be special ordered from a local fish store.


Author: Carrie McBirney, Clarice Brough, CFS
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