This fish is covered in mucus and has contracted what is known as brooklynella. Typical with clowns, it primarily attacks the gills first. At the onset, fish may scrape up against objects, rapid respiration develops, and fish often gasp for air at the surface as the gills become clogged with mucus. Very quickly the fish will become lethargic, refuse to eat, and its colors will fade which explains the rapid breathing.
Also notable is is the heavy amount of slime that is produced by a fish that has contracted this parasite. As the disease progresses, a thick whitish mucus covers the body. This will usually start at the head and spread outward across the entire body. Skin lesions appear and it is not uncommon for signs of secondary bacterial infections to arise.
For treatment, place the clown in formalin at a higher concentration, followed by continued treatment in a prolonged bath of formalin at a lower concentration in a quarantine tank (QT). Of course, the longer the fish are exposed to the formalin treatment, the more effective it will be at eliminating this disease. A form of formalin is quick cure.
