Sometimes, your freshwater fish get sick. If you notice signs of illness, try the following remedies — most of them applications you use in the whole tank — to treat your sick fish:
Salt: Common table salt is generally used to treat ich and other parasitic diseases.
Methylene blue: Used to treat diseases such as ich, fungus, and velvet.
Malachite green: Use this wonderful medicine to treat velvet, fungus, and ich.
Formalin: A bath-type treatment only, it should not be used in the main tank. A great remedy for parasites, it doesn’t work well on internal infections and can be very toxic.
Penicillin: Treats bacterial infections and is non-toxic.
Tetracycline: This antibiotic is great for bacterial infections and is non-toxic.
Acriflavine: Treats ich and fungus, but may turn water green.