Cardinal fish with a white fuzzy spot

[reece3689]

My Cardinal has a fuzzy white spot on his side. He eats great and has no issues.

 

[Idoc]

Possibly Lymphocytosis by the location on the fin. I'd watch for other signs of things occuring. Lymph is a virus that will typically resolve with good water conditions and healthy diets. Lymph should not show any other signs of distress on the fish, though...so if rapid breathing occurs, etc..., then it is something else.