Well my medicine cabinet contains the follows and the does the follow as well.
API Furan 2: for fungal infections, gill and pretty much most outside infections.
Metronidazole: use for treating flagallets or hex. Very effective when the infection is present and I suggest to buy as much of it as you can. (I get mines from Jemhco.com)
Hikari PraziPro: for use when flukes, tapeworms and other worms are detected. ( can't remmeber the names on the label) very effective but very expensive as well.
Aquarium salt: some people use non ioded table salt, because it's cheaper. I use it to treat any disease before adding chemicals to my water along with elevated temperatures.
Epsom salt: use for bloating and to aid fishes to pass dead tapeworm or whe constipation occurs.
HTH