Praziquantel Powder is a highly effective medication when treating flukes and flatworms in both freshwater and saltwater environments.  Can safely be used on sharks.  Praziquantel is safer than most other anti-parasitic medications.
10 grams will treat 950 gallons.
Non-toxic to live plants
Does not affect nitrifying bacteria
Safe to use with fish fry
Praziquantel is the active ingredient in several products, including Hikari PraziPro, API General Cure and Parasite Guard
 
Effective Against: Gill flukes, liver flukes, skin flukes, schistosoma (parasites of the blood), flatworm, tapeworm, turbellarian worms.  Does not treat pinworm or roundworm.
 
Treatment: Remove active carbon, Purigen, ChemiPure or other similar media that would remove medication from the tank. Turn off UV Sterilizers as well. Dosed at 1/4 teaspoon per 40 gallons of water after a 25% water change. Leave in aquarium for 5-7 days.  Recommended to do a second treatment to ensure all parasites have been killed.  Do not treat for more than 20 days straight
Not easily water soluable and can be mixed with ethyl alcohol or vodka.  May be repeated if necessary.
Treatment works best when activated carbon is removed from tank.