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Related FAQs: Zoanthids, Zoanthids 2Zoanthids 3Zoanthid ID, Zoanthid Identification 2, Zoanthid ID 3, Zoanthid ID 4, Zoanthid ID 5, & Zoanthid Behavior,   Zoanthid Compatibility, Zoanthid Selection, Zoanthid System, Zoanthid Lighting, Zoanthid Feeding, Zoanthid Health, Zoanthid Reproduction

Related Articles: Sea Mat: An Ocean Of Color For The Aquarium by Blane Perun,  Water Flow, How Much is Enough

/The Conscientious Reef Aquarist

Mostly Colonial & Very Hardy;

The Sea Mats & Polyps That Are the Zoanthids; part 4 

To: part 1, part 2, part 3,


By Bob Fenner  

Genus Protopalythoa:

Protopalythoa sp. Polyps as flat oral discs... 1, 2, 3 cm. in diameter (thought to be species specific). Tentacles on stalks, knob-like on polyp margins. Western Pacific. Here in N. Sulawesi, Indonesia. 

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Genus Zoanthus:

Zoanthus pulchellus, the Mat Zoanthid. Green, brown flattened discs of up to dime size with tan tentacles. Also from the Caribbean, the every-now-and-then offered. Below, in a back reef setting in Tobago and St. Thomas, U.S.V.I.
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Though Zoanthids are generally received and offered in good shape most everywhere, there are a few guidelines I'd adhere to in picking them out; mainly re appearance and symbiosis.

Choose specimens that exhibit all their polyps open; not necessarily all at the same time. Ignore ones with visible dead, whitish material. If they've recently been "separated" from a mother colony, give the new piece time to heal before purchase.

Healthy specimens that are colored should be deep and consistently so; those with their Zooxanthellae in decline should be avoided.

Symbioses: Many Zoanthids live in close association, either commensal or mutualistic with other species, particularly sponges and algae; and they "get along" with most other kinds of sessile marine life as well; neither quickly overgrowing them or being supplanted by true corals, other Zoanthids, Corallimorpharians or even some anemones. Regardless of their innocuous nature, Zoanthids should be purchased without their symbionts. Die offs from specimens purchased with sponges and algae are way too common. To repeat; the exception to the rule of Zoanthid hardiness is the ones that come attached to commensal sponges and algae. Many of these perish easily.

Environmental Conditions:

Water Chemistry and Physics: The sea mats and polyps that are Zoanthids are far more tolerant than other cnidarians to waste accumulation and otherwise less than ideal water conditions. Nonetheless, minimal nitrate (less than 10ppm), phosphate (one ppm) and undetectable ammonia and nitrite should be your target.

Circulation: Practically speaking, Zoanthids cannot receive too much water movement. Such flows should be chaotic; that is, not consistently blasting from one direction.

Lighting: Many of the species of Zoanthids kept by aquarists are hermatypic, living with endosymbiotic Zooxanthellae within their tissue. These forms appreciate moderate to intense lighting; either metal halide or shallow placement in settings with adequate full-spectrum fluorescents.


Introduction/Acclimation: New specimens should be "drip acclimated" underwater and, if possible quarantined for a good two weeks, or longer, until all polyps show signs of reconstitution and feeding.

Predator/Prey Relations: These polyps capture small suspended crustaceans, not large life in the wild and "in captivo". Likewise, they are decidedly shunned by would-be pests and predators. It turns out their tissues bear potent poison (Palytoxin). Fishes and predatory invertebrates give them wide berth with one exception. There are some known predaceous snails that consume Zoanthids. If you find these on your colonies, they are simple to remove.

Reproduction: Though Zoanthids reproduce sexually much as do the true corals, the most common form is asexual. Under regular conditions, very frequently you'll find a piece of material at the base of a colony gives rise to a new individual; a reproductive method termed gemmation.


Even the "green" Zoanthids with internal algae helping them make their food require supplemental feeding. Most successful reefers feed their Zoanthids every day or two with either a mash of small Zooplankters blown over the animals with a turkey baster or some solid, meaty foodstuff placed on the polyps. It's best to subdue circulation at this time; done practically with a timer.


Other than absolutely dissolving and falling apart, Zoanthid "disease" is difficult to diagnose. Some or all polyps staying closed all the time with their tentacles enfolded is a danger sign. Here you should look to you water quality and consider effecting a large (50% or more) water change if all else checks out.

One other "environmental disease" should be mentioned. For folks using metal halide lighting in shallow water, a white bumpy condition on Zoanthid oral disks has been linked with excessive light. Affected specimens need to be relocated to less bright, deeper conditions.

There are proponents of the use of iodine as a preventative and treatment for this group; within moderation such dips and periodic additions should do no harm.


For reef livestock period, few organisms can match the Zoanthids for hardiness and longevity. Their tolerance for "challenged" spaces and conditions where they occur naturally is mirrored by their success in captive settings.

New reef aquarists, or those uninitiated with keeping stinging-celled life should consider this group and the Corallimorpharians for "practice" before moving on to such groups as the true/stony corals or anemones. Other than initially selecting healthy specimens and providing them with brisk current and adequate light, there is very little to the husbandry of these polypoid Cnidarian animals.

Bibliography/Further Reading:

Barnes, Robert. 1987. Invertebrate Zoology; 5th ed. Saunders, Fl. 893pp.

Fenner, Bob. 1992. Cnidaria: Stinging celled animals. FAMA 7/92.

Fenner, Bob. 1996. A diversity of aquatic life; Coral anemones: Order Corallimorpharia. FAMA1/96.

Fenner, Robert. 1998. The Conscientious Marine Aquarist. Microcosm, VT. 432 pp.

Gosliner, Terrence M, Behrens, David W. & Gary C. Williams. 1996. Coral Reef Animals of the IndoPacific. Sea Challengers, Monterey, California.

Gutierrez, Santiago. 1991. From a reef's point of view; Zoanthus. FAMA 12/91.

Humann, Paul. Reef Creatures Identification; Florida, Caribbean, Bahamas. New World Publications, Inc. Jacksonville, FL. 320pp.

Mancini, Alessandro. 1992. Zoanthidae in tropical marine aquariums. FAMA 3/92.

To: part 1, part 2, part 3,

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