Thanks for the very thorough reply. I appreciate your detail and now feel that I have a good course of action. As I believe that I have the snowflake type of hydroids, I will proceed with the Panacur option in my dwarf tank. As I do have live rock and the gorgonia in my big tanks with my mustangs and hybrids, I think I will leave them for the time being. It’s good to know that the panacur will also kill the bristleworms, which despite care in curing everything before it goes into the system, still seem to have found their way into the tanks.