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   Button Polyps Zoanthus sp. are among the easiest corals to keep. They are almost always a first coral for new hobbyists, and highly recommended for beginners. They can be very colorful, with numerous color morphs ranging anywhere from a brown, to bright green, turquoise, yellow, orange, red. and more. Keeping them under a largely actinic lighting makes them appear to be glowing in the dark!

   This coral has a fairly short stalk topped with a flat oral disc. The tentacles of the Button Polyps are delicate and radiate from the outside of the disc. The polyps can be connected to each other, but they primarily form mats, called coenenchyma. However they do not incorporate sand or sediment in the coenenchyme, as other Zoanthids can.

   The Zoanthus genus is one of many types of polyps, that the catch all term, “Zoanthid” is used for. Common names for this particular genus include Zoas, Zoanthids, Sea Mat, Zoanthid Button Polyps, Green Button Polyps, Green Sea Mat, and Button Polyps. There are many incredible aquacultured Zoanthus with very creative names to describe them, mainly to excite a buying response. Be sure to check the genus on specimens with unique names like “Giant Super Pink Flamingo Zoanthids” or “Ringed Zoanthids” if you want to be sure of what you are getting.

   Zoanthids require water currents to bring food and can also be fed small amounts of suitable foods, (zooplankton, brine shrimp nauplii) but will do well without feeding. A strong light source is required for Button Polyps to do well. Be cautious of filamentous algae as it will overgrow and smother polyps. Typically the blue colors tend to be a little “harder” to keep if there are less than 4 or 5 polyps on a frag.

   Button Polyps are not an aggressive species. They can be kept in the company of small coral reef fish and shrimp. Good tank mates include small tangs, blennies, tilefish, sword gobies, damselfish, and dottybacks. But avoid large crustaceans, large angelfish, and most butterflyfish as they like to nibble on their tentacles. The Button Polyps are a great beginner’s coral, yet they add interest and beauty to any reef aquarium with the many uniquely colored specimens available.

Scientific name

   Family: Zoanthidae
   Species: Zoanthus sp.

Distribution / Background

   Zoanthus Coral Information: The Zoanthus genus was described by Cuvier in 1800. There are about two dozen nominal species in this genus. These include some Atlantic Ocean species such as Z. pullchellus and Z solanderi, some Pacific Ocean species such as Z. coppingeri, Z. mantoni, and Z. vietnamensis, and the Zoanthus found in both oceans like Z. pacificus and Z. sociatus.

   Common names the Zoanthus genus is known for are Zoas, Zoanthids, Sea Mats, Zoanthid Button Polyps, Green Button Polyps, Green Sea Mat, and Button Polyps. Some aquacultured Zoanthus have unique names, mainly to excite a buying response such as “Giant Super Pink Flamingo Zoanthids” and “Ringed Zoanthids”.

   Where Zoanthus Corals Are Found: The Zoanthus genus are common and widely spread in both the Atlantic and Pacific Oceans.

   Zoanthus Coral Habitat: The Zoanthus sp. habitat includes shallow tidal areas, lagoons, back reefs, and many other reefal areas. They are also found in deeper waters, which is where the fluorescent orange varieties are located.

Status

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

Description

   What do Zoanthus Corals look like: Zoanthus sp. have soft bodies covered with a leathery skin, called the cuticle, which gives them protection. Their polyps have fairly short stalks topped with a small flat oral disc. Delicate tentacles radiate from the outside of the oral disc and are usually expanded day and night. The oral disk has a mouth, or siphonoglyph, in the center that leads into their stomach cavity. This cavity has vibrating cilia that helps to exchange water and to feed.

  The polyps of the Zoanthus genus are not usually larger than 1/2″ (1.25 cm) across the top. The polyps can be connected to each other and they primarily grow as mats. However their mats do not incorporate sand or sediment in the coenenchyme, as other species of Zoanthid can. Zoanthus species come in all sorts of colors from browns and grays to bright orange, red, yellow, green, blue and many color morphs. On some, the oral disc can be a contrasting color from the tentacles.

   Descriptions for some of these types of Zoanthids:

  • Zoanthus pacificus
       This Zoanthid forms clumped colonies of polyps with short tentacles. They are found in shallow areas where there is high water movement. Their colors are varied. The oral disc is generally a different color than the “skirt”, and even a third color can form in the very center, almost like a pupil.
  • Zoanthus sociatus – Sea Mat
       The Sea Mat grows in linear colonies (rows) that form mats, and usually have green to turquoise polyps. They are found on reef flats and can also be found partially buried in the sand at times. They have short tentacles and feed on detritus. They need high light levels due to their natural exposure to full sun during low tides. This Zoanthus has a larval, crawling stage, which allows them to crawl on the substrate before attaching.
  • Zoanthus pullchellus – Zoanthid Button Polyps
       The Zoanthid Button Polyps grow in circular mats that are so dense, the polyps press tightly against each other. They are mostly brown, but can have other colors and have short, blunt tentacles. They can be found in very shallow waters as well as deeper waters where orange varieties are found.
  • Zoanthus solanderi
       These Zoanthids also form dense mats. They are very fast growing colonies on reef flats and back-reef areas. They will overgrow other corals if not kept in check.
  • Zoanthus coppingeri
      These small polyp colonies grow very large over coral rubble, and will grow over the Velvet Finger Montipora Montipora digitata. These polyps develop in very bright colors such as green, yellow, orange and red. They love bright lighting and good current, as indicated by their natural habitat, which are reef flats and rocky shores.
  • Zoanthus mantoni
       These Zoanthids are green, grayish blue, or dark brown and green. They bury their mat in silt and substrate and will sometimes grow near Protopalythoa. The disc has a white pattern that is very attractive against their contrasting tentacles. They are found in lagoons, so they like a low current and bright light, although they are tolerant of many aquarium conditions.
  • Zoanthus vietnamensis
       These form sheet-like mauve or blue thin, rubbery mats in which their polyps are almost completely buried. They have short tentacles that contrast in color with the rest with light blue, or blue-green oral discs. They inhabit shallow, high water flow areas, and also can be found growing with Palythoa and Protopalythoa.

Difficulty of Care

   Zoanthus Coral Care: The Zoanthus genus is easy to care for as long as they have adequate lighting and good water flow. They are a recommended beginner’s coral. Typically the blue colors tend to be a little “harder” to keep if there are less than 4 or 5 polyps on a frag. Be cautious of filamentous algae as it will overgrown and smother polyps.

   There are a couple of cautionary items to be aware of when you keep Zoanthids:

  • Palytoxin
      The members of the Zoanthidae family have varying degrees of poison called palytoxin. All of the Palythoa genus and most Protopalythoa genus produce a high level of this poison in their mucus and gonads. Other genera, such as the Zoanthus genus, have it to a lesser extent, and so a less dangerous degree.
       To be affected by this toxin, it must either be ingested or must enter the bloodstream. It can enter the system through an open wound. It has been suggested by some that it may also be absorbed through skin contact though this is not confirmed.
       The danger to the aquarist is minimal with proper precautions. If you have a cut on your hand, this poison can get into your system, but in average aquarium keeping it is unlikely to pose any danger beyond a localized skin reaction. Some hobbyists wear gloves when handling these organisms.

    Here’s a couple interesting facts!
       Fish that eat Paly polyps, like the filefish, can bring this palytoxin in to the human food chain. This would be when a predator of the filefish is a fish that is typically eaten by humans.
       Also, Pacific tribes used to use this neuromuscular poison to paralyze enemies and prey animals by coating their spears with the mucus of these corals.

  • Vibrio Infection
       Vibrio can at times be in the coral mucus, thus causing a Vibrio infection in humans if care is not taken. Most people have no problem, but caution and common sense play a role here. Wearing gloves and possibly goggles may be the safe route to go. After handling a Zoanthid, make sure the mucus is not on your glove or hand before handling any other corals!

Foods / Feeding

   Zoanthus Coral Feeding: In the wild, Zoanthus 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.

   In captivity the Button Polyps largely depend on their zooxanthellae for energy. They will need bright lighting to supply this type of nourishment. They largely feed on bacteria, algae, and dissolved organic material. They can also be fed small amounts of suitable foods such as zooplankton or brine shrimp nauplii, but will do well without feeding. Most of the Zoanthus genus do not eat large pieces of food.

   Some Zoanthus have been known to respond to different foods, depending on the species. In some species only certain zooplankton prey will elicit a capture response. For instance, Z. sociatus will seize sea urchin eggs, but other species will not respond at all to sea urchin eggs.

Aquarium Care

   Stable tank conditions are needed to keep the Zoanthus 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. Make sure iodine is present, and also the addition of trace elements may help with the Button Polyps survival.

   Suggested levels for Zoanthus species are:

  • Calcium:  380 – 430 ppm
  • Alkalinity:  3.2 – 4.5 MEQ/L (8 to 11 dKh – 10 is recommended)
  • Phosphates:  0, zero.
  • Magnesium:  1250 – 1300 ppm.
  • Strontium:  8 – 10

Aquarium Parameters

Quick Reference Chart
Lighting:Prefers Low Lighting LevelsPrefers Medium Lighting LevelsPrefers High Lighting Levels
Water Flow:Prefers Low Water Flow LevelsPrefers Medium Water Flow LevelsPrefers High Water Flow Levels
Temperament:Peaceful TemperamentSemi-Aggressive TemperamentAggressive Temperament

   A typical live rock/reef environment is what is needed for your Button Polyps, along with some fish for organic matter production. A mature tank (well over a year old) is advised to increase the successful keeping of Zoanthus.

   Provide proper lighting and water movement. Moderate water flow and a strong light source are required for Button Polyps to do well. These colonial anemones are not an aggressive species. They get along well with their own kind, but space should be provided between them and other more aggressive corals.

  • Minimum Tank Size / Length: 10 gallon Nano (38 L) or larger
  • Marine Lighting: High
  • Temperature: 72° – 82° F (22° – 27° C)
  • Salinity / Specific Gravity: 1.023 – 1.025
  • Water Movement: Moderate
  • Water Region: All areas of the aquarium

Compatibility and Social Behaviors

   The Zoanthus genus will get along with itself, but does need to be placed in an area where they will not encroach on nearby corals. They will only bothers corals that are too close. They are not toxic like the Palythoa or Protopalythoa, but can simply smother corals by growing over them.

   Button Polyps are not an aggressive species. They can be kept in the company of small coral reef fish and shrimp. Good tank mates include small tangs, blennies, tilefish, sword gobies, damselfish, and dottybacks. But avoid large crustaceans, large angelfish, and most butterflyfish.

Sex – Sexual differences

   No sexual difference in appearance is known.

Breeding and Reproduction

   The Zoanthus genus has a reproductive cycle of spawning along with other corals. This is an amazing event. It has been seen in the Great Barrier Reef during the week after there is a full moon in the month of November. (Ryland & Babcock, 1991) They can be hermaphrodites or separate sexes. The sperm and egg meet and then form a larva that swims, called Zoanthina. (Delbeek & Sprung, 1997) The Zoanthus genus will also bud from their base.

   Propagation is rather simple for Zoanthus corals, simply cut the mat or chip away under the polyp’s grip. They can be out of the water a few minutes with no ill effects. Dry the bottom of the mat or debris that the polyp is stuck to, and the rock or plug you will be putting it on. Then use super glue (the gel is the best) to connect them. Wait a few seconds for it to set and then put the new frag back into the water. Another method that can be used is to rubber band them to a rock or desired surface. By the time the rubber band breaks away, the zoanthid will have connected.

Potential Problems

  The Zoanthus genus is generally hardy and durable if provided with a proper reef environment. However be cautious of filamentous algae as it will overgrown and smother polyps. There is a snail called the Box Snail or Sundial Snail Heliacus areola that prey on Zoanthid colonies, so must be removed if seen. Also avoid large crustaceans and aufwachs feeders, such as large angelfish and most butterflyfish, that like to nibble on their tentacles.

Availability

   Zoanthus Corals for Sale: The Button Polyps or Sea Mat Zoanthus sp. are very easy to find at pet shops and on line. Online they can run about $6.00 up to $50.00 USD or more for a small grouping, depending on the color and size.

References

Featured Image Credit: Sandeep Gawade, Shutterstock