Freshwater dip works really well for parasitic removal, mainly white ICH. It does not work well for black spots, which i dealt with before and best way is to phsically scratch off the parasites with your finger. Personally I think fresh water bath is better than copper quartine tank. Quartine tank is hassel and copper takes at least 7 days to work. If a fish is healthy to begin with, the fresh water bath will remove almost all parasite, but with such "relief" removal, fishes often fight off the remaining parasites on their own, provided if they are fed with healthy nutrition.
Preventing any disease and parasite from happening is actually quite easy. Just make sure your fishes get good diet. I recommend Kent's Zoe vitamin too. When fishes are healthy they dont ever get sick to begin with. There is countless number of bacteria and parasite in my fish tank anyways but when fishes are healthy and their immune system working, they dont ever get sick. UV steralizer can weaken fishes immune system and might harm berlin systems such its indiscriminte killing can kill good bacterias too.
Stress cause alot of sickness too. It is a good idea to warm up the new water in water change, many people often wonder why their fishes get sick after water change, it is the temperature. Never use live food, they are parasite bombs.
If your tank allows, a cleaner shrimp would be wonderful.
