Liv2padl,
And so I become the receiver of the flame. I was only answering his question instead of talking down to him, setting him up for the "oh your water quality and fish keeping skills are horrible," and throwing the fix-all clean water answer at him. Yes clean water will help but what he described is most likely Hexamita, his water parameters will only tell you how fast he can expect his oscars to die from a secondary bacterial infection. A picture is what we need to be fairly certain that it is Hexamita. Hexamita is a parasite, where do you suppose it came from if not from another tank. I did not mention that goldfish are also carriers of Hexamita, so feeders could have been a source but it does not matter because either way it is most likely that once Hexamita is ingested it will infect the fish and is inevitable. Again clean water may have helped prevent the outward rotting and slowed internal infection, I don't think that anybody knows for sure since Hexamita is still sort of a mystery and infected fish can die without showing rot, but his fish are already in the advanced stages and he needs medication recommendations. Why ask for water parameters if all you are going to do is recommend regular water changes and testing anyway. Just make the recommendation along with medication.