Praziquantel is, and always has been, the "treatment of choice" for Flukes (trematodes) in fish. Praziquantel does not require water changes, praziquantel is harmless to fish of all species including Koi and goldfish fry, and is nontoxic to plants, and praziquantel has no negative filter impact.
The recommended dose of Praziquantel is 1 gram per 100 gallons of pond water.
The drug is simply stirred vigorously into a liter of clean water and, when mostly dissolved, the white colored suspension is deposited into a high-flow area of the pond. If the fish ingest some of the medicine as it settles out, it's not a problem. Discontinue carbon and UV during treatment to avoid inactivation of the Praziquantel. You do not need to bypass the filter nor worry about oxygen levels during treatment. The most successful treatments are deployed in cleaner ponds, so any
excess leaf litter or debris should be removed. Clearance of the flukes can be determined by the overall improvement of signs of flashing and scratching. On occasion, segments or ribbons of worms may be passed in the fish stools and are of no concern to human health
The advantages are that Praziquantel is entirely benign to plants, fish and filter while clearing the Flukes and intestinal worms out rapidly and completely, even with fry.
Now, it can be considered that praziquantel is the least-expensive Fluke treatment for ornamental ponds. When you consider that it requires only one or two doses and does NOT require water changes, or plant removal, nor increased water agitation.