The oceans are full of creatures capable of killing us; one of the more surprising marine menaces is a group of popular aquarium corals known variably as “button polyps”, “palys” and “zoas”. Rather than biting us in half or injecting us with some venomous barb, these nefarious creatures secrete a highly lethal chemical called palytoxin. This is information which is oftentimes not related properly to new aquarists, whether purposefully or through sheer ignorance or negligence on the part of retailers. Undoubtedly, there are many in this hobby who would avoid purchasing such a dangerous organism were they to be made aware of the risks. There are also likely some reading this right now who are looking at the zoas in their tank with a leery eye and pondering what to do. It is important to understand that palytoxin is not present in every species of “zoa”. I have heard many knowledgeable aquarists incorrectly state that all “zoanthids” contain it and are therefore dangerous, which is not accurate whatsoever. Such blanket statements show a lack of expertise in these corals and the extensive research recently published on them. One such study (Deeds et al 2011) focused on aquarium specimens and found that there is likely a single lineage of button polyps which is truly dangerous to the general aquarium community. This makes proper identification of the utmost importance, so lets jump into the esoterica of invertebrate taxonomy and attempt at last to correctly identify these deadly corals and their harmless relatives.
Common aquarium “zoas”: Zoanthus sansibaricus, kuroshio & gigantus. Note the white pots of the latter.
First and foremost, if your button polyps are a bright and colorful red or yellow or orange or pink, you are not in any danger. The vast majority of such specimens which enter the trade are either Zoanthus vietnamensis or Zoanthus sansibaricus. The abundant red and green zoas exported from Vietnam are the latter, and these are apparently lacking in palytoxin at any detectable level. The relatively common pink zoas are likely to be Zoanthus kuroshio, which is likewise a safe addition to your reef tank. The species most commonly referred to as “palys” in the aquarium trade are actually Zoanthus gigantus, which, if the general trend holds, can be presumed to be safe (though confirmation is needed). These are a bit larger than the previous species and come in a variety of unique and popular color patterns.… More:
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