I use Tropic Marin's Pro Coral Cure on any new corals I buy, it is a special blend of lugols with other nutrients added to cure corals and kill parasites, and have had no bad mishaps since I have been using it. Anywho...the best thing I have tried on zoas is a 1/10 oxygen peroxide mix with tank water dip. Gotta be careful though, the H2O2 will bubble up the zoa's tissue and hurt it if left in there too long. That dip did wonders when I had almost 10 colonies get white fungus. Reason I did the peroxide was that I read about it on a forum elsewhere...not gonna say where because I honestly can't remember.....either way 1/10 parts was reccommended, but if you are careful enough you can go higher just gotta be careful.