Can anyone tell me what this growth is on the face of one of my Harlequin Rasbora please, and what I need to do to treat it? I also have a colony of red cherry shrimp in the same tank so any treatment needs to be copper free. Thanks for any advice.
I'm not seeing anything untoward other than the fish's nostrils/nares. Water quality consistently at 0 ammonia, 0 nitrite and 20 nitrates ought to help most issues resolve. You may also find either API Pimafix or API Melafix helpful, depending on what it is that you're seeing.