I do have feather dusters. What will it do to them?
It will kill worms, which also is likely your target (in the fish). If you are hesitant about dosing the tank, put him in a basket, feed him a lot to get him eating and then start feeding him food that has been soaked in prazipro. Then it is more targeted at just your fish. Make sure he is already eating though before you try this.

