wow how sad.... looks like its scales are wasting away... rotting .. being eaten.. have you treated it with any medicine.. does he eat? check all your water perimeters.. any other fish affected.. how long has he been this way.. have you added any fish..do you feed him live feeders... he was beautiful ... got to figure out what happened.. all i could find was MOUTH ROT
SYMPTOMS: The flesh is eaten away around the mouth.
TREATMENT: This is caused by a fungus or bacteria. It can be treated with Fungus Eliminator, Maracyn, MarOxy or Binox. It can be spread to other fish and other aquariums by using the same net.