How about telling us the sypmtoms? Or have you seen anything specific? There are various parasite. And Clout can treat internal as well as external. But really depends on what you are dealing with. Pictures of the affected fish?
My fish is an armatus which is very active and "healthy" looking. The only thing is that he bearly eats and there is a whitetish thing that sticks out of his bum. He is just a tad skinny. I saw whitish yellow poop here and there this week. He just ate yesterday.