top of page

Zoanthids :


From Wikipedia, the free encyclopedia


Zoanthids (order Zoantharia also called Zoanthidea or Zoanthiniaria) are an order of cnidarians commonly found in coral reefs, the deep sea and many other marine environments around the world. These animals come in a variety of different colonizing formations and in numerous colors. They can be found as individual polyps, attached by a fleshy stolon or a mat that can be created from small pieces of sediment, sand and rock. The term "zoanthid" refers to all animals within this order Zoantharia, and should not be confused with "Zoanthus", which is one genus within Zoantharia.


They are among the most commonly collected coral in reef aquaria, easily propagating and being very durable in many water conditions.


Nomenclature controversy :


The name of the order is controversial. Non-specialists often use the term Zoanthidea whereas most taxonomists use Zoantharia. The term Zoantharia in turn is used temporarily instead of Hexacorallia. However, major taxonomic papers published since 1899 by specialists (O. Carlgren and F. Pax have described more species than all other authors combined) use Zoantharia, and most recent specialists on the order   continue to use the term Zoantharia.




Zoanthids can be distinguished from other colonial anthozoans and soft coral by their characteristic of incorporating sand and other small pieces of material into their tissue to help make their structure (except for the family Zoanthidae). The main characteristic of the order is that their tentacles are organised in two distinct rows.


While the most well-known zoanthids are the zooxanthellate genera found in tropical and sub-tropical waters (primarily Zoanthus and Palythoa), many other species and genera exist, some still relatively unknown to science.  Many zoanthids (in particular the genera Epizoanthus and Parazoanthus) are often found growing on other marine invertebrates.


Often in zooxanthellate genera such as Zoanthus and Palythoa there are a large number of different morphs of the same or similar species. Such zooxanthellate genera derive a large portion of their energy requirements from symbiotic dinoflagellates of the genus Symbiodinium (zooxanthellae), similar to many corals, anemones, and some other marine invertebrates.


Families and genera:


The families and genera within the order Zoantharia (also known as Zoanthidea) are:


            -Abyssoanthus Reimer & Fujiwara in Reimer, Sinniger, Fujiwara, Hirano & Maruyama, 2007


             -Epizoanthus Gray, 1867


              -Hydrozoanthus Sinniger, Reimer & Pawlowski, 2010

              -Terrazoanthus Reimer & Fujii, 2010




             -Antipathozoanthus Sinniger, Reimer & Pawlowski, 2010

             -Corallizoanthus Reimer in Reimer Nonaka Sinniger & Iwase, 2008

             -Isozoanthus Carlgren, 1905

             -Mesozoanthus Sinniger & Haussermann, 2009

              -Parazoanthus Haddon & Shackleton, 1891

              -Savalia Nardo, 1814 (synonym: Gerardia)


              -Palythoa Lamouroux, 1816




             -Isaurus Gray, 1828

             -Zoanthus Cuvier, 1800


Note: there are some zoanthid genera such as Neozoanthus or Paleaozoanthus for which there are currently only few data available, those zoanthids having never been found again since their original description.


1 2 >3

Aquaria :


Zoanthidae include many species popular in the fishkeeping world, among hobbyists and professionals. They are relatively easy to keep alive and healthy, and will often spread to cover rocks in their bright circles of color. They are known by some as carpet coral, button polyps, and "zoas" or "zoos."


Dangers :


Some zoanthids contain the highly toxic substance palytoxin. Palytoxin is one of the most toxic organic substances in the world, but there is an ongoing debate over the concentration of this toxin in these animals.[citation needed] However, even in small quantities, the toxin can be fatal should it be ingested or enter the blood stream. If delivered immediately, it has been suggested that vasodilators can be injected into the ventricle of the heart to act as an antidote.  A 2010 study found toxic zoanthids in three Washington D.C. area aquarium stores. 


Reports are varied and conflicting on the potential dangers of handling the animal in the aquarist hobby. General opinion and practical experience holds that in order for this toxin to be dangerous to humans, the average aquarist would need to ingest the zoanthid in sufficient quantities, or brush a recent cut over it, and average handling, propagation and aquarium maintenance is unlikely to pose any danger beyond a localized skin reaction.


Other sources state that palytoxin can be absorbed through intact skin,  and the danger of acute poisoning from venomous zoanthids is quite real. According to a report an aquarist was poisoned through skin injuries on fingers by a species of Parazoanthus, but recovered after 3 days. His zoanthid was found to contain 2-3 milligram of palytoxin per gram.[18] For comparison, the intravenous LD50 dose of palytoxin for a grown man is less than 8 microgram. Thus each milligram of the offending zoanthid contained enough venom to kill at least 125 grown men.


Palytoxin has also been known to damage the eyes of aquarists who attempt to propagate the coral by cutting it and being squirted in the eye. temporary blindness and permanent blindness have been reported. It is always recommended to wear proper eye protection when cutting.


Research shows that in sublethal quantities, Palytoxin is a tumor promoter, and is being studied in relation to signaling pathways in skin cancer genesis.


Generally it is considered proper practice to always wear appropriate protective gloves when reaching into salt water tanks and handling sea invertebrates.


Diet : 


Zoanthids feed both by photosynthesis, aided by the zooxanthellae they contain, and by capturing plankton and particulate matter. Although photosynthesis aids in their nutrition, even species that do not actively capture plankton cannot live through photosynthesis alone.  Zoanthids can eat meaty foods, such as lancefish, brine shrimp, krill and bloodworms. 


Zoanthids are without a doubt some of the most popular soft corals for beginners and experts alike. Fast growing, super hardy, and available in every color of the rainbow, they are easy to keep and fun to collect. New and unusual color morphs are always being sought, but even the 'common' variants often possess stunning colors.


Other soft polyps, such as Palythoas, Yellow Polyps, Xenia, and Star Polyps are all very similar in requirements to the Zoanthids and are equally hardy. All of these soft polyps are easy to frag. Most grow by encrusting mats or runners over the liverock to which they are attached. This can then be cut inbetween polyps, usually with little harm to parent or frag.

Care Level :



Aggressiveness :

Low to moderate. Generally not prone to stinging their neighbors, although they can grow so quickly that they overtake slower growing corals. Many do put chemicals into the water that can irritate other corals, so diligence in water changes and carbon use may be especially beneficial in a mixed reef that includes them.


Lighting Requirements :

Low to moderate, although many will do fine under stronger lighting if properly acclimated first.


Water Flow:

Moderate. Excessive flow may prevent them from opening fully.


Tank Placement:

Low to mid.


Water Quality:

While every effort should always be made to provide good water quality for your tank inhabitants, these corals are generally quite forgiving of temporary lapses and in fact may adsorb some of their nutritional needs directly from the water. This hardiness makes them idea for newer tanks still getting established.


Special Notes:

Some of the chemicals produced by Zoanthids are potentially harmful to humans. Use care when handling them, especially if fragging. Wearing gloves is always the best way to be safe when working with reef livestock.

Keeping and Caring for Zoanthids


courtesy to : By Julian Sprung



Foods and Feeding :


One of the most satisfying aspects of caring for zoanthids is watching them feed. Because they have such large polyps it is easy to observe them capturing food and ingesting it. Using a turkey baster or similar device one can directly place food onto individual polyps, and they will slowly close over it. This is particularly true for species of Palythoa and with yellow polyps, but also for some species of Zoanthus.


There are Zoanthus spp. that don’t seem to take foods that one would expect them to eat, and these apparently depend more on their zooxanthellae for nutrition than on feeding. All zoanthids are able to feed on fine particulate and dissolved matter, which they can trap in their surface coating of mucus.



Zoanthids occur in a wide range of tropical and subtropical habitats, but they are typically found in reef flats, sandy hard bottoms, rocky shorelines and tide pools. Many species occur in the intertidal zone, where they are completely exposed to air at low tide.


Some species are also common on hard substrata, such as coralline algae or clam shells scattered among various types of seagrass. Although these shallow habitats are good places to find them, zoanthids can also be found on any hard substrate on a coral reef to considerable depth. Some species, the giant-polyped Palythoa grandis for example, are most common in deep water, below 80 feet.


Predators and Disease
Some fishes will eat zoanthids, though most find them distasteful. The box snails (Heliacus spp.) feed specifically on zoanthids, and can be considered a pest if one is trying to grow zoanthids, or a savior if one is trying to rid aquaria of zoanthids.


Heliacus spp. are not always easily seen, as the shell is round and about the size of a closed zoanthid polyp. As with most cnidarians, there are seaslug predators of zoanthids. These present a real threat to captive populations because they can reproduce quickly and rapidly decimate colonies. Careful quarantine is necessary to be sure to avoid introducing such pests.


The common “brown jelly” protozoan infections that affect corals can also kill zoanthids and can spread from zoanthids to corals. If a section of zoanthids remains closed, deflates, and then develops a clear brown gelatinous mass over it, carefully siphon off the mass and cut out the affected polyps. Give the colony a short 1-minute fresh water bath, if possible, and then replace it in the aquarium with a strong stream of water over the colony to prevent reinfection.


Newly imported zoanthids often come associated with encrusting sponges. When the sponges are damaged by shipping and handling, they die and rot, promoting anaerobic conditions within the rock and among the zoanthid polyps. This has a telltale rotten-egg smell and often is associated with white films produced by bacteria of the genus Beggiatoa.


These white films may suffocate zoanthids along with the fouling sponge. It is important to inspect newly imported zoanthids and remove any loose dead or dying sponges. Also, because sponges within the rocks commonly die, the newly imported zoanthid colonies should be placed where they receive extremely strong water flow, to ensure that the rocks are well oxygenated to prevent anaerobic conditions.

Zoanthids occur in a wide range of tropical and subtropical habitats.    



courtesy to : 

Zoanthid and Palythoa are both colonial type corals, meaning they form a colony of individual polyps all living together.  They are commonly referred to as zoas and palys. As they are very similar corals, I have combined them into one article. Zoas and Palys are both very hardy soft coral placing them amount the easier to keep corals and making them a excellent choice as corals for beginners.  These corals can come in some spectacular colors and color combinations, among the most amazing colors to be found in any soft coral.  For these reasons, they are kept by  advanced and new hobbyist alike.   I have also added star polyp corals and glove polyp corals into this article as they are also colonial corals with very similar requirements and hardiness when compared to zoas and palys. The below will outline the requirements to keep these corals healthy and thriving in your tank.


Some General Guidelines for Zoas and Paly Coral Care


While they can tolerate a wider range of water parameters, this will not remove your responsibility to provide the best water conditions that you can as detailed below
Salinity: 1.025 to 1.027
Temp.: 77 to 79 degrees F.
Nitrates: below 5 ppm  is best for long term health, however they tolerate much higher levels for a period of time.
Phosphates: below 0.05 ppm
Water Flow:  Between moderate to low flow but not directed at the coral
Lighting: Moderate to Low.  Some can handle higher levels of lighting if properly acclimated
Alkalinity (dKH), Calcium, Magnesium, and pH, all should be balance with each other as described in the below link:

As neither zoa or palys have a calcified skeleton structures, they can be more tolerant of swings in the alkalinity, calcium, and magnesium when compared to other corals.  However, they will not be very tolerant to swings in PH, Temp, or salinity which is no different than any other coral or fish.


These are among the more tolerant corals to different  levels of lighting.  These corals contain zooxanthellae inside their body, they will be able to get most of their required nutrients through your tank lighting.  This is why it is important to have the correct levels of lighting in your tank and to watch for signs that your lighting levels may not be correct.  These corals  can also get nutrients from the water in the form of  microplankton and zooplankton and will benefit from the occasional spot feeding.  They  will do best when they get their needed nutrition from both the water and your tank lighting.  They are not tolerant of higher flow rates.  If it looks like the heads are not fully opening, try placing them in a area with lower flow.


Most corals have a natural defense mechanisms to protect themselves. Zoas and Palys have are the least aggressive when it comes to defensive abilities.  Often, the opposite can be said about them.  They can quite frequently become damaged and even start losing heads when they fall victim  to another coral’s sting or exposed to those toxins.  In addition, the protective slime like coating that is on the zoas and palys are a favorite delicacy among the “coral nipping” fish.  The corals typically dies when a fish removes the outer slim coating from the coral.


Some types of zoas and palys can grow so fast that I would even state they are a invasive coral that can take you’re your tank it your let them. Zoas and palys do best when attached to the rocks.  There should a adequate space place between them and other corals depending on the other coral’s requirements.  The slime coating on some palys can also be toxic to humans so please, handle these corals with care.


Some Examples of Zoas and Palys :


Zoanthideas :


These corals come in a very wide range of colors and color combinations.  Some zoas can have up to three different colors on them: one around the outer edge of the head, one on the head, and a third in the center of the head.  Zoas stay fairly small in size (less than 1 inch) but the colony can easily grow and expand.  You have to be very careful with the compatibility of reef safe fish and zoas in the same tank.  These will typically be the first corals to suffer from a coral nipping fish.  The pictures above are of a few different zoas in my tanks.

Palythoas :


As with zoas, palys can come in a wide range of colors and color combinations.  While the heads can range in size from ½ to 2 inches, the colony can grow at a fairly fast pace.  The slime coating on some palys are among the most toxic to humans so please, handle these corals with extra care.  The above pictures are of a few palys that I have in my tanks

Clove Polyps (Clavularia sp) :


While these are not a zoa or paly, I have included them here as they have the same requirements as zoas and palys,  and can often mistakenly assumed to be a type of paly.  They only get to about 2 to 3 inches in height and have a head size of about ½ inch.  The heads can have a bright almost neon coloring to them while the tentacles branching off the heads can have a colored line running down the center of them.  The heads can retract into the base of the coral making it look like a purple lumpy spot on your rocks. These are among the fastest growing corals that I have kept.  When kept in the correct conditions, these corals will take over your whole tank if you allow them to grow uncontrolled.  The above picture is of the clove polyps that I have in my tanks.

Star Polyps :


Once again, these are not a zoa or paly, I have included them here as they have the same requirements as a paly and can sometimes be mistakenly assumed to be a type of paly.  These corals can grow on your rocks as well as on the sand and on the glass of your aquarium.  They grow almost like a carpet of small polyps that only have a height of about ½ to 1 inch and a head size of about ¼ to ½ inch.  The heads of these corals can completely retract into the base making it look like a think purple coating on your rocks. Green is the most common color to find this coral in.   I have read they can be found in other colors, but I have only seen them in green and pink.  The above are pics of green star polyps and pink star polyps in my tanks


Button Polyps, Colonial Anemones, Sea Mats, Stick Polyps


courtesy to : 


Zoanthids are a choice beginner's coral. They are extremely hardy, durable, and can be incredibly colorful as well!

Zoanthids are generally a very undemanding coral. Zoas are some of the hardiest and most durable inhabitants for the reef aquarium. They are easy to keep and make a wonderful beginner's coral. Take good care of them and you'll be rewarded with a beautiful display!


 Zoanthids are commonly referred to as Button Polyps, Colonial Anemones, or Sea Mats. They resemble clusters of miniature sea anemones, often growing like a mat across a hard substrate. But although they may look similar in appearance to anemones, they are much smaller, with their oral discs barely reaching 1 - 2 cm in diameter.


Zoanthids are very attractive colonial anemones. They can make a colorful addition to the hard surfaces of the reef aquarium. They come in all sorts of colors from browns and grays to bright orange, red, yellow, green, blue and many color morphs. Yet the coloration seen on Zoanthids is usually not a product of their own pigments. Rather it comes from a marine algae, zooxanthellae, that live within their tissue. As this algae needs light to thrive, so do the colorful Zoanthids!


Easy to Keep Zoanthids :


 In nature zoanthids are often found in turbid, high-nitrate areas in canals, harbors, inter tidal areas and reefs. For this reason they are fairly tolerant of poor water quality or high nitrates, phosphates, and dissolved organics.


 It is easy to keep most of the species of Zoanthids found in the aquarium industry. Yet there are some species that live in conjunction with sponges or other invertebrates. At one time these Zoanthids were thought to be parasitic, but now it is believed that they actually work in a mutualistic relationship, each benefiting from the arrangement. Keeping these specialized species is more difficult as you must keep their companion alive as well.


A normal reef environment is needed to keep most colonial anemones. Zoanthid care includes proper lighting, good water movement, and regularly feeding. Also provide hard surfaces for these sea mats to encrust such as live rock, regular rock, dead corals, or pieces of porous ceramic. They will not do well if filamentous algae is allowed to grow in the reef aquarium, as they can be smothered by it.


Zoanthid Care :


Like most sessile organisms, these Button Polyps need good water flow to bring food and help rid them of waste. Many species live symbiotically with the marine algae, Zooxanthellae, which need light to thrive. The species that contain zooxanthellae require a strong lighting source. Those that do not contain zooxanthellae don't require the strong lighting but will not be adversely affected by it.


Tank Mates for Zoanthids:


In a well-established aquarium, Zoanthids can be kept with fish and a number of other invertebrates. But they will compete for space they just like other colonial and sessile encrusting invertebrates. They don't have a very strong sting, so are at a disadvantage there, but they are fast growers, so can often overtake their neighbors. When it comes to placing zoanthids next to Corallimorphs, (mushroom anemones), the zoanthids almost always lose. Always place these kinds of corals a good distance away from each other. 


There are several fish species that will dine on zoanthids. These fish include the Raccoon Butterflyfish, Chaetodon lunula, which have been used recently to eat aiptasia, many filefish (Monacanthidae), and Sharpnosed Puffers (Tetraodontidae).



1 2 >3

bottom of page