I posted a thread on here about a week ago with no responses so I am posting another one. MODS, please feel free to merge threads! I believe that I am dealing with a case of parasites in my 36 gallon tank. I first noticed that my female platy was scratching, soon followed by one of my young zebra danios. Looking this morning, she has lost a noticeable amount of weight and appears narrow. Another one of my platys has stringy poo (which may or may not be related.) I have corys in the tank and have never experienced anything like this before so I am unsure on how to treat the tank. Is ParaGuard safe for use with corys? Is there another alternative? Please, please help because I'm afraid it will spread throughout the tank.