If there is no known problem and you are just treating a new fish or something i allways treat 2 times. So for this I add 1 tablet for each 10g of tank size. And then wait 48 hours and add another tablet for each 10g of tank size. And then do not do a water change for a week. ---------------------------------------------------------------------------------------This is for a hospital tank. If you are treating your main tank then do not follow this regiment. The parasite clear will kill the benificial bacteria in your tank at the package reccommended high doses. If you are treating your main tank then i use half a dose so 1 tablet for each 20 gallons once a week. And do a water change before the next dose. I do this for a month.