Zoanthids are not immune to predators and disease, which is obvious from the occasional problem of zoanthid eating nudis that many aquarists deal with from time to time. Most likely, zoanthid eating nudis come from the Pacific Oceans, specifically around the Solomon Islands.
Although vicious predators, zoanthid eating nudis are also known as being particularly beautiful, and use the undigested nematocysts of the zoanthids as a defense mechanism against their own predators.
Natural Defense to Nudis
Zoanthid eating nudis are quite resistant to predators, most likely because of their quick abilities to adapt to their predators. There are however a large number of specific species of fish that can pose a threat to zoanthid eating nudis, specifically wrasses and butterfly fish, but unfortunately these fish are not suitable for most home aquariums due to their size, price, and other attributes.
Safe from Nudis
There are a small number of zoanthids that actually do not appeal to zoanthid eating nudis, so certain zoanthid polyps will be at higher risk of attracting zoanthid eating nudis than others. Generally speaking, it is more common for zoanthid eating nudis to prey upon the Zoanthus genus versus the Proptopalythoa or Palythoa genus.
Treating Nudis In Reef Aquarium
It is very difficult to rid a colony of zoanthid eating nudis once the manifestation has taken hold. One method to try and eradicate zoanthid eating nudis in a colony is fresh water dips of the entire colony. However, this needs to be done frequently (once or twice a week until the zoanthid eating nudis are gone), as it takes more than one fresh water dip to kill zoanthid eating nudis and their eggs. It is also recommended to diligently assess the zoanthid polyps for zoanthid eating nudis and to pick out the eggs sac and adults with tweezers or other fine combed method.
When purchasing zoanthids, avoid acquiring colonies whose polyps are not completely open, as zoanthid eating nudis could be a threat to that colony. If possible avoid purchasing long skirted zoanthids and instead concentrate on the short skirted specimens from Fiji, Tonga or Solomon Island. Some aquarists have suggested that zoanthid eating nudis prefer long skirted varieties because the overhang helps the zoanthid eating nudis to hide from possible predators. There is preventative action you can take to avoid predators like zoanthid eating nudis, among others, from infiltrating home aquariums. The answer is to quarantine every new coral specimen that is being added into the tank, just as is done for new fish.