I think in New Zealand, folks correct me if I'm wrong, you need something called Wonder Tonic...could be the wrong name. Somebody tell her the name of the cure for ich.
When treating for ich, you must remove the carbon (if you have any in your filter, as the carbon will remove the meds). The treatment for ich only kills the "parasite" after they fall off the fish. Follow the directions for the treatment and follow exactly as it reads. For example, the stuff I bought here, luckily haven't had to use it in over 2 years! Anyway, I had to do a 25% water change, treat, then so many days I think, treat...anyway, all the treatments must be kept up till all visible signs of the ich are GONE! Meaning that you usually treat for a period of time after there is no more white spots on the fish. Geesh, does that make sense?
Caper