Meds I have used: 1) salt: on rare occasions for badly torn fins or cuts 2) dimilin: used a few times to treat incoming piranha with anchor worms (also good for argulus). one treatment does the trick. 3) Praziquantel (a dewormer for dogs but works well on fish that have tapeworms). Haven't used it yet, but good to have just in case... Also very effective in treating gill/body flukes. Kills through paralysis. 4) Formalin/Malachite Green: used to quarantine feeders for a week. 5) Betadine (similar to liquid iodine) to disinfect wounds like badly scraped chins or open ulcers. 6) Potassium permanganate: basically a nuke that will kill everything (bacteria, fungus, parasites). It oxidizes any organic matter. I use it as a last resort for heavy infestations. Not to be used in the tank (will quickly kill all nitrifiers). Fortunately, haven't had to use it yet...
I prefer not to use meds, but if at all possible, salt would be the first course of action for me. But it is not very effective against anchorworms, argulus, flukes. Thus I keep the supplies handy just in case.