The fish looks stressed so there is something going on with him. If this is not normal and a new thing for him have you done anythign new, new equipment, food, tank mate etc etc. What are the water parms and the last time the filter has been cleaned. Also temp of the tank.
yeah as a few said
he is not feeling all right
how old is he
have you found any change in color
change in behavior
and change in the size of the nuchal hump
hes like 10 months old or something and i think its because he used to be the big boss dogg in the tank but i added a rd and a jag and he doesnt mind them just acts like a lil ***** now..
he eats only when hes really hungry or when i feed him bloodworms. and i did a water change last week