Remove all invertebrates - these are extremely sensitive to medication. Turn off UV filters, and ozone filters, and remove chemical filtration like MatrixCarbonand Purigen. Ensure that your tank is fully cycled and stable; poor water quality is the root cause of most fish diseases, and adding medication will do no good if the water chemistry is still bad.
Use 1 measure (included) per every 40 L (10 US gallons) of water. Repeat this dose every 72 hours for a maximum of 2 weeks. Repeat every 3 days for up to 2 weeks or until symptoms disappear. Use whenever introducing new fish.
When the treatment period is over, PolyGuard can easily be removed using activated filter carbon like MatrixCarbon. It does not linger in the substrate or filter media of the tank.