I had these for about 8 months. Came in on a urchin of all things. Spent a lot of money on Flatworm eXit. They were immune to it. Tank had both a six lined wrasse and 3 yellow tail damsels in it. Those did not eat the flatworms. At some point I replaced the yellow tail damsels with Azure damsels as the yellow tails were beating up a much more expensive new to tank yellow tang. I noticed almost right away that Azures were eating the flatworms. I no longer have flatworms.