Bichir with fat belly

[KatReza]

I was given a bichir and a few other fish by a friend, not knowing much about them. I've had him for a few months now and he has developed what looks like a beer belly. It has sometimes seemed to get slightly larger or smaller, but never goes away (this could be my imagination). An aquarium FB group I am in suggested that he may have eaten some gravel and to get him into a bare bottom tank. I finally was able to get one for him and have now noticed some red on one side of his beer belly. I don't know if it related or maybe he scratched himself on one of his hiding spots, but I didn't notice it before.
Does anyone have any idea what might cause this belly?

 

[kno4te]

Hard to say. Could be due to swallowing a piece of gravel or snail shell. This is also seen in cb polys.....kind of like a hernia related to eating. Gets bigger with food and shrinks once digested.

How is acting? Is it eating? How ur water parameters? Prior tank had gravel?

Would suggest moving the Senegalus to a qt tank and adding some Epsom salt 1 tbsp per gallon and some triple sulfa. Would not feed the fish for now. See how the redness and bulge responds to this.

 

[KatReza]

He's acting and eating normally. Water parameters are all good, except nitrate went up, I was a bad fish mom and got lazy with water changes (but he had this long before that). I have corrected that problem. I use the freshwater master test kit. Yes, my main tank has gravel.
I have Epsom salt, may have to order triple sulfa. I will look at what I have in my fish pharmacy when I get home.
Thank you for your advice.