My Oscar has a large open red sore, on the left side of his face just in front of his eye. This problem has been ongoing for two months. I have checked water levels. PH,acid, nitrates, everything is in the normal range. I have used a number of meds, myracin, melaxflix,erythromycin, tetracyclin, and metronidazole. None of these meds have helped. He still has a good appetite, and I have been doing water changes every week instead of every other week. George is in a 72 gallon tank by himself with a RENA water filter. Any help would be greatly appreciated. Thanks for any help.