Are his scales sticking out like a pinecone if you were to look at it from the top?
if it is the fish probably has dropsey.
from what i've researched there is no treatment for this problem and it can be caused by many things from bacteria to improper diet which leads to digestive problems.
It is a build up of body flood that normally causes the bloating and scale protraction.
Depending on the cause of the disease it can be fairly contagious
but not to put your hopes down for your fish, someone else probably knows alot more than me about this subject and will hopefully come forward with a reply!