Zoanthids

All Photo credits: Michelle Stuart Coral Credits: Michelle Stuart
Zoanthids are wonderfully coloured animals which are often to as colonial anemones, corals or button polyps.  Zoanthids come from reefs all around the world and in a variety of different colonizing formations.  Their ease of care and colourful appearance make them ideal candidates for a novice reef keeper.  However, hidden within these beautiful creatures is one of the most potent neurotoxins found anywhere on earth, and new reef keepers need to be made aware of their hidden dangers.

Health warning: 
Zoanthids contain highly toxin called palytoxin. Extreme care needs to be taken when handling these deadly creatures.  Palytoxin is fatal, even in small quantities, if ingested or gets into your blood stream and there is no known cure for it. 
When propagating any type of Zoanthid, make sure you have a dedicated workstation and thoroughly clean all equipment used, especially if any of the polyps should break open.  Do not let children or pets around Zoanthids, the water they have been kept in or anything they come in contact with. These chemicals are the only thing that Zoanthids have to protect themselves from would be predators.

Water Quality and Tank Size:
Zoanthids are fairly forgiving of water quality however for long termed health and stress reduction within a colony it's best to keep the water conditions as stable as possible.  Zoanthids are generally found in water temperatures between 24C (75F) - 29C (84F), salinity should be kept at 35ppt or SG 1.025, pH 8.2 - 8.4, alkalinity 3.2-4.5 meq/L (7 - 12 dKH), calcium 450ppm, phosphates < 0.1ppm*, and nitrates < 10ppm*. A good protein skimmer is also highly recommended to keep dissolved organic matter (DOM's) relatively low. Due to the small sizes of Zoanthids, they are idea candidates for nano tanks as well as the supper large reef tanks as space fillers. 

* <  means less than, > means greater than.

Lighting:
Lighting an important aspect of keeping a healthy vibrant colony alive and growing.  Zoanthids contain symbiotic photosynthetic algae called zooxanthellae. They are tolerant of a wide variety of different lighting conditions from relatively low lighting to being able to handle metal halides.  However photosynthesis alone wont be enough to keep a colony fed properly. 

Feeding:
Although most species of Zoanthids rely heavily on photosynthesis for their primary source of food production, they are also capable capturing food from the water column.  Some Zoanthids will feed during the day, others at night, most can and will feed continuously closing only in response to external stimuli.   Determining what to feed or even whether to feed Zoanthids is a difficult task due to the wide range of species which have yet to be reliably identified.  Zoanthids will feed on phytoplankton, plankton, small particulate foods, and dissolved organic matter.  Target feeding isn't necessary unless you don't have any fish or other means of adding food to the tank.
Without proper nutrition available polyps will often shrink in size and slowly fade away or become detached from it's mooring to drift into what would potentially be a better location for the polyp to grow.

Location:
Figuring out where to place a polyp in a tank really isn't all that difficult.  They are relatively unfussy in terms of water movement and lighting. Colonies are amazingly adaptable and will begin to morph to make best usage of their location.  However, there are a few guild lines to help find a location where the colony will be able to establish itself and expand.
Avoid putting them in shady locations or where other corals will eventually grow large enough to block out their lighting.  Don't place them in an area of extremely high water flow. Some colonies prefer being placed in at the bottom of the tank in a sandy location.  Allow room for growth.  Once a colony is established in a location it likes, it will grow rapidly and can even start to grow over nearby corals.  If you want to limit the area that they grow on, placing a rock in the middle of an open area in the tank is the easiest way to limit their expansion. Once you have placed the colony, avoid moving them as much as possible, they could become stressed and not open up for a while or cease to grow. Don't put them near corals with a strong tendency to sting or it could decimate the colony.

Zoanthid Health and Predators:
Diagnosing disease in corals is difficult at the best of times and Zoanthids are no exception.  Often the only real indicator that something is wrong is when the individual polyps stay closed for long lengths of time or the entire colony closes up tightly for an extended period of time.  There is also very little knowledge of what can be done to help heal an ailing colony.  The first thing that should be done in the case of the entire colony closing up is look to water quality, chances are there is some sort of irritant in the water or some water parameter out of balance. In this case, a large scale water change of 50% is highly recommended.
If the colony starts to wither and individual polyps float away from the rest of the colony try moving the colony to a different location where they would get better lighting and more food floating around them.  If they continue to wither away, it will be necessary to remove the colony from the tank to prevent the contamination of the water. 
When Zoanthids close up and start to develop white spots or what looks like burn marks, normally in tanks with extremely intense lighting like metal halides, they are expelling their zooxanthellae algae. This will most likely occur when a colony is first introduced to a tank with drastically higher lighting conditions or when light bulbs are newly replaced.  Make sure you acclimatize them to the lighting as well as water parameters.  To light acclimatize a colony place it as far from the light as possible for about a week and then slowly move it up a couple inches at a time each week until the colony is where you would like it to finally rest.
A nocturnal predatory snail called Heliacus sp is occasionally found on newly imported wild colonies of Zoanthids. These snails have a unique conical operculum that retracts as the snail retreats into it's shell for protection against predators.   The shells are round and flattened in shape for easier movement within the mass of the colony.  These snails should be removed as soon as they are noticed and a careful examination should be made for small snails hidden in the colony.
Another predator is a nudibranch that is difficult to notice.  They are highly evolved to mimic the appearance of a partially closed polyp with a few tentacles sticking out.  They are brown in colour and can slightly alter their colouration to better reflect the colony in which they are feeding.  As they feed on the Zoanthids, they are able to retain some of the polytoxins to use in their own defense against predators.  Care should be used when removing these nudibranches so you don't come in contact with the neurotoxin.

Growth:
They can be found as individual polyps, attached by a fleshy stolon or a mat that can be created from pieces of sediment, sand and rock. There are a large amount of different morphs of the same or similar species depending on the location on the reef each colony occupies.  Different species are even able to cohabitate the same area and even join stolons creating a unique and colourful colony.
As the colony spreads, it's possible to encourage it to split or frag by placing small rocks near the mother colony and cutting the stolon once a few polyps have attached to the new surface, by breaking the rock that the mother colony is on apart or but carefully peeling back a part of the stolon and gluing the new colony to another piece of rock.
The photo to the left is a newly fragged colony of Zoanthids.  After two months in the tank, the colony has started to spread out across the rock as seen in the photo to the right.  This rapid growth shows that I chose a good place for the colony within the tank.  They are getting good lighting, a medium indirect current, food particles are easily accessible and water quality is optimal.
Below is a colony that started out with about 20 polyps on a small rock that was placed in the centre of a larger rock.  8 months later, it has spread across the original rock it was on and all over the larger rock around it.  I have propagated this colony and documented the process on the page "Zoanthus Frags."

The different Genus:
Although these colonial animals are generally blanketed under names like Zoanthids, button corals or seamats there are more then one genus available for sale.  All the little corals were originally thought to be members of the same genus and was only later discovered that there were at least six common ones commonly available in the trade.  Identification of Zoanthids down to species level is extremely difficult without bisecting a polyp.

Acrozoanthus: (stick polyps)
These polyps are small with long stems and commonly grow on the tubes of featherdusters.  They are both filter feeders and photosynthetic.  Most of the time they are sold on a tube without a living featherduster in it which will become a problem as the biodegradable tube isn't being maintained and will eventually dissolve leaving nothing for the polyp to attach to.  Once the host has died off chances of survival is fairly slim.

Isaurus: (snake polyps, tube polyps)
Although rarely seen in the hobby they are slowly becoming more popular as people are able to better care for these unique polyps.  They form long tube-like stems and can grow either individually or attached by stolon.  They have small tentacles that tend to extend more at night then during the day when they feed on microscopic phytoplankton.  However, they also contain symbiotic zooxanthellae for additional food production.  They are generally found in shady areas of the reef and come in shades of grey, yellow, green and brown. 

Palythoa: (sea mat, Button corals)
Members of this genus has the highest concentration of palytoxin and should be handled with extreme caution.  These are the second most common genus found in the hobby. They are naturally found on reef flats and lagoons.  Their stolon is comprised of all manner of sediment and particulate matter. These are often single coloured polyps which are broad flat discs and very short tentacles.  The colony rarely gets bigger then 30cm (12") before it breaks apart and forms new colonies.  These polyps are capable of minor calcification so ensure the calcium levels in the tank are properly maintained. They reproduce by forming buds at the edge of the stolon as opposed to the base of the polyp.

Parazoanthus: (yellow polyps, colonial polyps)
The most common Parazoanthus available is the Yellow polyp which are often confused for brightly coloured glass anemones.  These often grow in small clusters of polyps which will quickly break apart to form another small cluster. Some species are found growing on and feeding off other organisms such as sponges or tubeworms; without their host animal, chances are they wont survive long.  Other species of this genus don't contain any zooxanthellea and therefore require target feedings. They reproduce by forming small buds at the base of the polyp.

Protopalythoa: (Sea mat, button corals)
Members of this genus are very similar to the Palythoa and debate is still ongoing about whether or not they should be classified in the same genus.  The main difference between the two is the Protopalythoa polyps are generally found as individual polyps not attached together by a stolon and they generally have more tentacles around the oral disc. They reproduce by forming buds at the base of the polyp.

Zoanthus: (sea mat, button corals)
These are the most commonly available and most highly sought after of all the Zoanthids available.  They vast array of colours, fast growth rate, ease of propagation and high adaptability make them a must have for any reef keeper from novice to advanced. These spread primarily by sending out little buds at the base of the parent colony. The polyps rarely exceed 25mm (1/2") in diameter and generally have a short stock close to the stolon.  Elongated stocks indicate that they aren't getting enough light for photosynthesis.  The stolon does not incorporate any sediment or particles. 

Expanding your collection   All photos taken by Michelle. Button polyps (Zoanthus) are one of the hardiest coral that I have come across.  They can tolerate fluctuations in water chemistry better then any other type of coral and are great for people just starting a reef tank.  They multiply rapidly and quickly spread from rock to rock.  The easiest way to get button frags is to place a rock beside the main colony and they will spread onto the new rock.  Once enough buttons are on the new rock it is easy to cut the two rocks apart and you are done.  But what if your colony is starting to move on to a rock you don't want it on or you want to split a colony you already have into a whole bunch of smaller colonies to sell later on?  Here I have done just that.  I have taken some of the buttons that are spreading around the tank and created three new colonies. Equipment Required: Rubber Gloves Rock rubble Crazy glue (Super Glue UK) 1 Razor blade or very sharp scissors paper towels A container of clean saltwater to put the cutting in A container of clean saltwater to hold the main colony A note of caution: Zoanthus contain a powerful neurotoxin that can be fatal if ingested. Make sure that you wear gloves when handling them and dispose of the gloves immediately after use.  Keep your work area clean, and disinfect everything that is used afterwards.  It's better to be safe then sorry. Here is the colony that I will be making the first cutting from.  Some of the buttons are getting ready to grow onto a rock that I don't want them on, so I'm going to remove that part of the colony and glue it to a new rock. Dry off the surface of the rock that you wish to place the new colony on in preparation for the glue.  The glue will be added just after the colony has been cut away from the mother colony.   As you can see the buttons are already starting to grow onto another rock.  When I try to lift the main colony up, there is a small piece of fleshy material connecting the colony together.  I cut the colony apart at the thinnest possible area attempting to do as little harm to the colony as possible.  The small part of the colony that is left, is then peeled away from the rock to be prepared to be placed on the new rock.   Now that the fragged colony has been cut away from the rock, I add some glue to the rock it's going to be placed on.   Then I dry off the bottom of the colony so that it can sit in the glue and get the best hold possible.   After the bottom of the colony is dried off, I position on the new rock it will call home.  I let the glue set for about 20 seconds before putting it back in the water and rinse off any slime that comes from the colony.   The colony was then placed back in the main tank where there is good lighting and good water flow.   This is the colony approximately one hour after the new colony was returned to the display tank.  It's already beginning to open up, showing that they feel comfortable in the new location.  I will continue to keep an eye on the colony to make sure it opens all the way.   This is the colony 5 hours after it's was put back into the tank. Most of the buttons in the colony have opened up.  If the remaining buttons don't open up within 24 hours, I'll consider having to remove them so they don't rot and infect the healthy polyps within the colony.    This is the same colony one and a half months after being fragged. They are well established and spreading across the rock.  The rock has also matured and you see some different types of coralline algae's growing on it as well.