So just surface parasites etc huh, something I never bothered to question (which is rare lol). Copper as you mentioned as well as others in this thread, is probably the most effective treatment out there for "ich", but for some individuals, its not the most practical due to monitoring it as live rock and sand can interfere with readings/dosing. Last I remember, copper can and does weaken the immune system of fish and of course has the ability to kill fish, which I remember a co worker years ago successfully achieve. My other concern using just copper is secondary infections that can occur from the parasitic infection, so that should be closely monitored as well. I used to use primarily, quick cure which is a little medley of medications, malachite green and formalin, its inexpensive, works and easily acquired. The medication metronidazole that I recommended, can also be fed to your fish. This topic can go on, but the lesson as so many have pointed out is, quarantine your livestock which will save you some headaches and hopefully keep your fish happy!