More info needed:
1. tank size
2. ammonia & NO2
3. Size of fish, age
4. tank temp
5. any lumps, spots, dots, raised scale, bloated abdomen or swelling of body?
6. how long had this been happening?
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.