Zoanthids (order Zoanthidea) are a type of soft coral commonly found in coral reefs all 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 pieces of sediment, sand and rock. There is a large number 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. Like most corals, they are hermatypic and obtain much of their nutrient requirement from symbiotic unicellular algae called zooxanthellae, and so are dependent upon a light source for nourishment. As a result, these corals are usually found not far beneath the surface. The lighting requirements of Zoanthids vary from species to species, but as a whole they are less demanding than other corals available to the aquarium trade.

Zoanthids (eg Montlivaltia) are known in the fossil record from the Triassic period onwards. Many familiar forms such as the Madrepores have survived essentially unchanged for many millions of years.

Zoanthids contain the highly toxic substance palytoxin. Palytoxin is the most toxic organic substance in the world, but there is an ongoing debate over the concentration of this toxin in these animals. However, even in small quantities, the toxin can be fatal should it be ingested or enter the blood stream. There is no known anti-toxin.

In order for this toxin to be dangerous to humans, the average aquarist would need to ingest the zoanthid in sufficient quantities. Average handling, propogation and aquarium maintenance is unlikely to pose any danger beyond a localized skin reaction.

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