Hardy Coral for the Aquarium
Zoanthids Are the Perfect Saltwater Aquarium Starter Coral
May 15, 2008
Zoanthids are small disc shaped polyps that come in a variety of remarkable colors and are the perfect “starter coral” for the new marine aquarist. They are hardy, low-maintenance and fast-growing animals from the taxonomical class Anthoza. This is very appropriate as the word anthoza translates from the Greek as “flower animal,” and zoanthids are animals that do resemble flowers.
Relationship to Other Corals
Marine biologists call zoanthids hexacorals because their tentacles come in multiples of six. Other common hexacorals include sea anemones, mushroom corals and stony corals. While sometimes called “soft corals,” zoanthids are different from the true soft and leather corals. Soft and leather corals are octocorals with eight tentacles per polyp instead of six.
While zoanthids are related to stony or “true” corals that possess hard skeletons, zoanthids do not have a skeleton. Some zoanthids are solitary animals with a single polyp attached to a rock or shell. Other zoanthids are connected by runners called stolons, and still others are embedded in a tissue matrix or mat. This tissue matrix is called a coenenchyme. Nearly all of the ones commonly kept in the aquarium reproduce quickly through budding at the base of the polyp.
Deadly Zoanthids?
Zoanthids, like all animals in the class Anthoza, are cnidarians, which simply means that they have stinging cells. These stinging cells, called nematocysts, assist with food capture, but are not generally responsible for stinging humans like a jellyfish. Instead, some zoanthids create mucus that contains a toxin called palytoxin, which is one of the most deadly marine toxins. This is why it is essential to wear gloves when handling zoanthids, especially zoanthids from the family zoanthidae. This includes species from the popular Zoanthus, Palythoa and Protopalythoa genera.
While some zoanthids do possess palytoxin, it is uncommon for aquarists to become severely ill as a result of handling the animal. You would need to consume sufficient quantities of zoanthids to cause a life-threatening reaction or have the toxin enter your bloodstream. Indigenous peoples of the Indo-Pacific did, in fact, use palytoxin from zoanthids to coat spear tips, and a wound inflicted by such a spear was usually fatal. In the case of the aquarist, the toxin can enter the bloodstream through a cut on the hand, and this is why it is important to wear gloves whenever handling zoanthids.
Symbiotic Zoanthids
Most zoanthids that the marine aquarist will come across in the hobby are symbiotic animals known as zooxanthellate. In other words, most zoanthids kept in marine aquaria possess symbiotic algae called zooxanthellae within their tissue and, as a result, can sustain themselves through photosynthesis so long as they are provided with appropriate lighting. All zooanthids also rely to varying degrees on particulate food and plankton capture to sustain their metabolism. It is therefore a good idea to target feed your zoanthids at least once a week.
In short, zoanthids are ideal marine aquarium animals. They are hardy, fast-growing and long-lived, and while some do contain a deadly toxin, it is easy to protect oneself from intoxication by simply wearing gloves. Provide your zoanthids with moderate to strong intermittent water flow, moderate intensity lighting and at least weekly target feedings, and in no time, these flower animals will be thriving in your mini reef.
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