IP are by far the most likely reason a fish can eat and not gain weight. The IP just take over, the more the fish eat the more the IP have to consume. Prazi is very low risk and I don't hesitate to add it to my ray system, I'd start it as per bottle directions. I believe epsom salts soaked flakes could help as well, though I'm not certain.
Thank you. I don't know why my brain couldn't comprehend that the fish could have parasites and still be eating, like a dog with worms. Makes sense, thanks again!