One of my fiant danios from my 75-gallon Tank was gulping for air the whole day today. I caught him in a net (which was way too easy to do, indicating he was sick) and saw that part of his mouth was missing :0 It also looks like one side of his gills is redder than the other. Did he just get hurt or could this be a disease of some sorts? Initially I thought that my danios mouths were white as well but I'm not 100% sure they are. For now I've seperated him to my 10-gallon with a divider in the middle and am keeping him on the side with my betta fish. This is just so that I can monitor what's wrong with him.