How To Treat Crustacean (Visible) Parasites in Freshwater Aquarium Fish

CyroPro from Hikari is a chitin-synthesis-inhibitor like Dimilin, and what it does it interrupt the parasites' ability to make their own skin (exoskeleton) and that is fatal to the parasites. The anchor worm and fish lice parasite go through several "larval" phases before you see them on the fish and you kill those before they ever even show up on the fish. The 'adult' anchor worm simply dies because it can't even make a decent egg case. 

This product Eco Labs LAWP seems to have the greatest economy, and is easy to get. Very safe to use, but it's no better or worse than Hikari's CyroPro pictured above. 
This is usually dosed ONCE or maybe twice. It is NON TOXIC to fish. But it's totally toxic to dragonfly larvae, crayfish, and any other 'insect' or 'crustacean' in the freshwater pond or facility so be careful and aware of the impact. Won't hurt snails at all. Won't kill tadpoles. 

Dimilin
Often, this is hard to get and the product at right is available only from "third party sellers" on Amazon but that's okay. This is usually dosed ONCE or maybe twice. It is NON TOXIC to fish. But it's totally toxic to dragonfly larvae, crayfish, and any other 'insect' or 'crustacean' in the freshwater pond or facility so be careful and aware of the impact. Won't hurt snails at all. Won't kill tadpoles.