A SAFE FLUKE TREATMENT AT AN AFFORDABLE COST! Also great for freshwater and saltwater aquariums. Praziquantel is the safest most effective medication on the market for treating flukes, it does not stress your pond fish or harm your  biological filter. Plus, Prazi is an excellent treatment for internal parasites and worms in goldfish, koi and tropical fish in fresh and salt water. All it takes is just one treatment of Prazi and there is no need to follow up with water changes. Treat with Prazi every spring to get your pond fish off to a great year!