Ok. You need to get him out of the of the 10 gallon, he'll pollute that in hours. That will not do anything with or with out meds. You do not need meds to treat this. The only cure is clean water, extremely clean water, and a good diet and it takes a long time. Put him in the 90 gallon even though it is too small for 2 oscars it's better than one in a ten gallon. (Maybe get another tank). Have a divider ready in case they don't get along. Change 50% at least of the water every 2 days. (Every day would be better)Feed a good pellet as the staple with occasional treats like blood worms, worms, insects ect.... but no feeder fish, to much risk of disease and they are not nutritious. Boyd's vitachem soaked into something like freeze dried krill and fed once a week will help too. Keep pounding the fresh water to him for 2-3 months and it will heal up slowly. Now once they have this they are much more susceptible to getting it again and will require clean water upkeep.
