Waterlife Parazin is for the treatment of Fish lice (Argulus), anchor worm (Lernea), gill maggots (Ergasilus) and other insect and crustacean parasites/predators found in aquaria.These can be so small that they are not visible to the naked eye and these paracitic preditors can be very detrimental and even kill.A single dose is usually all that is required to solve the issueParazin is safe with fish plants and filtration.Precautions:Before use Read instructions carefully.Switch off u.v. sterilisers and remove carbon and or ammonia removers. Replace after 10 days.Dosage:20 tab / Treats up to 450 litres.