You might want to confirm what you have via a microscope. See https://pondinformer.com/fish-lice-treatment-guide/ and https://www.ncbi.nlm.nih.gov/pmc/art...0diflubenzuron.
Amazon sells this, no idea how effective:Dimilin-X Koi & Goldfish Treatment: Anchor Worm Fish Lice Flukes diflubenzuron. Salt seems to help some as well as PP.