Another thought, someone mentioned "living with Ich" perhaps he/she is right, not every parasite survives to get on a fish. That being said, perhaps the best approach is a multi pronged approach. 1 boosting fishes immune system as in ginger or garlic 2 water quality 3 UV sterilization 4 protein skimmer must remove some of the parasite from water column 5 filter feeding animals. Surely this all has an impact on the Parasite population. Living SoCal and growing up with dogs and cats we always battled fleas, my mother would vacuum every day and washed the dogs every week, it was the best way to control them before medications like front line. Thank goodness for that stuff! Maybe in a reef tank it's the same thing keep it as clean as possible, protein skimming, UV, nutrition and filter feeding animals. Maybe all these things together are the answer. Many diseases in humans are fought this way.