Hello well one of my corys in my 5 gallon tank has fish fungus on it's left fin only nothing on the body am thinking he might have scratched his fin he's eating and swimming around. I have 2 cories in the tank and since I know fungus is contagious I picked up some Tetra fungus guard tabs and will treat the tank tonight with 1/2 tab and see how it goes wait the 4 days and see if I will need to retreat again after doing a 25% WC my filter sponge does not have carbon in it. The package says that décor can be stained by the tabs. Although this can happen I am thinking to leave the décor in the tank while treating it thinking can fungus live on these types of decorations & if so leaving them in the meds will help kill off whatever fungus might be on them am not sure about this any advise would be so appreciated