rot

Hey guys Just noticed this on one of my peacock bass Is this fin rot, or just an injury? If its fin rot, how to I get rid of it? ammonia and nitrite are 0, and nitrate is a bit high at 10 Thanks

Bought my silver dollar at a lfs who said a person came and dropped him off because they were going to throw him in the river. The lfs had him in a tank with africans convicts and dempseys. The fish were picking on him big time. So I took pity and bought him for $6 since his condition was bad...

okay... so was just out of town for a week, and came back home to one of my gymnogeos having a wierd face thing going on... half of it has turned black... straight down the vertical dividing line down his "nose", etc, then around back around his gill cover... it does not extend down to the lower...