Hey all, I've had this betta a year. She lives in an established 10 gal planted tank by herself, heated and filtered. I vacuum the gravel and do 50% water changes weekly. Last December I noticed she had a dark spot on her side. I posted pics to a betta forum and they all said it was just marbling. She was acting fine so I just let it go. Three months later the spot was getting larger and started spreading to her other side. I posted again asking if marbling should look like this. They said yes, that she could change colors many times before she was done. I wish I would've listened to my gut and got second opinions, but she acted fine so I let it go. A month ago I noticed that she was getting a lump with whitish stuff on her side where the black area is largest. She started acting poorly too, hanging near the bottom and occasionally darting around. Obviously NOT marbling. I did some googling and thought maybe it was columnaris. I purchased aquarium salt, added 1 tsp per gallon, and also bought API E.M. erythromycin. I followed the instructions on the box. She started perking up right away and acting normally again. The treatment period ended about 5 days ago and I put charcoal in the filter. I'm doing 50% water changes daily and testing for ammonia & nitrite because I assume the meds will kill the bio in the filter. She acts like her old self again, but I don't see any improvement to the black areas or the lump. I would appreciate any opinions. Thanks! How she looked in December 2014 How she looked in April 2015 How she looks currently. This was before treatment but there's been no change.