It looks badly bloated. I've never seen our pterodoras or other specimen in such a state so I'd think this is not normal.
I can't speak for all fish but I treated my tanks / entire populace in some tanks, including 4500 gal and 25K gal, with Epsom salt through feed. I didn't see any problems that I can remember now.
IME “armored cats” like granulous and irwini are pretty prone to bloat… stop feeding for a few weeks and it should subside. I had a large irwini that would do this from time to time over the years. It will take a cple weeks at the least to go back to normal. Watch how much ur feeding. Don’t stress it futher by switching tanks… divide it off in a section of your tank or use a floating rubbermaid type container to keep it in to prevent it from eating any more. I never used any additives, but as others have noted, epsom salts do help fish pass their bowls…
I've never seen one at all so I appreciate learning from you Rouben. This is an astounding bloat, if that's what it was. Were you able to determine what it was inside - water or some bodily fluid or... ?