Origin
To the best of our knowledge, our nasty little predators originate in the Pacific, notably the Solomon Islands.

Natural Predators
There are a number of fish that reportedly prey on zoanthid eating nudis, however, we’ve tried many and experienced a limited amount of success. We attribute this to the nudis’ ability to adapt to their predators, which we will discuss in detail later in this section.

All fish supposedly preying on nudis belong to the Halichoeres category of the Wrasses, and the Chaetodon family of the Butterfly Fish. Both have a number of downsides that make them unfit predators for most tanks.

Chaetodon: Too large for most tanks; preys on the same zoanthids you are trying to save; the most vicarious nudi eater, Chaetodon Semilarvatus, is, at $120 and up a pricey option.

Halichoeres: Not nearly as efficient as the Butterflies; suicidal jumpers; nudis seem to be an acquired taste that varies from individual fish to fish, many are not reef safe.

Zoanthid Hit List
Just like any other animal, nudis have preferences when it comes to food. Some polyps are much more likely to become infested than others. In general, your Paythoa and Protopalythoa (People Eater Varieties) will remain nudi free, even in case of serious infestations. Palythoa have too hard of a skin to eat or lay eggs in, Protopalythoa have on occasion found stray nudis getting too close to their tentacles to be a nice treat.

Next on the list of least likely to be affected zoanthids are Caribbean morphs of the zoanthus sociatus family. While closely related to Pacific zoanthids, we have observed very little infestation. This may simply be due to the absence of zoanthid eating nudis in Caribbean waters.

Extermination
As promised above, this solution will take 5 minutes and cost all of $20.00. First, get yourself enough Salifert Flatworm Exit to treat your tank two times. Each Package contains enough solution for 300 gallons of water. Then dose your tank according to instructions and watch the nudis turn inside out and die. Since the process does not kill eggs, you will have to repeat the process a week later. Since no adults are left to lay more eggs and eggs hatch within 3-4 days, you will have a 100% success rate. Additionally, since there are only few nudis in a system at a time, you won’t have to do any water changes to dilute toxins. (even a few hundred in a large tank is considered little compared to the number of flatworms you could have)

I’ve tried this method myself and seen others use it. It works! Grab a beer, lay back and savor victory.